Two geomagnetic storms occurred in October 2024, driven by the impact of a series of interplanetary coronal mass ejections (ICMEs) on the magnetosphere. The first was a moderate storm, with peak Sym-H near -150 nT, whereas the second was intense, Sym-H reaching -340 nT. We compare and contrast the magnetospheric dynamics in each case, using observations of field-aligned currents (FACs) from the Active Magnetospheric and Planetary Electrodynamics Response Experiment (AMPERE) and ground magnetic perturbations observed by SuperMAG. The first storm responded linearly to solar wind driving, quantified by a dayside reconnection coupling function, and displayed typical substorm dynamics. The response during the second storm suggests that the cross-polar cap potential (CPCP) saturated, and that the dynamics of the inner magnetosphere were complicated. Magnetospheric compression by high solar wind pressure during the second storm produced elevated FAC magnitudes, indicating that both convection and compression control magnetosphere-ionosphere coupling. We introduce a new FAC pattern complexity index which shows quantitively that the FAC pattern during the first storm largely retained the region 1 and 2 configuration associated with twin-cell ionospheric convection, but that during the second storm the pattern became more highly structured. We conclude that storm intensity should not solely be quantified by Sym-H but also by other aspects of the magnetospheric response to solar wind disturbances.
How to cite: Milan, S., Mooney, M., Bower, G., Hodnett, R., Amerstorfer, U., Möstl, C., Samsonov, A., Anderson, B., Gjerloev, J., and Vines, S.: Solar wind-magnetosphere-ionosphere coupling during the October 2024 storms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12981, https://doi.org/10.5194/egusphere-egu26-12981, 2026.
This study presents a comprehensive statistical comparison of solar wind measurements between the OMNI database (collected at L1 and shifted to the Earth's bow shock nose), and near-Earth solar wind observations from MMS, Cluster, and THEMIS missions near the bow shock nose. Using a threshold-based classification methodology, the analysis encompasses approximately 353 days (MMS), 283 days (Cluster), and 125 days (THEMIS) of solar wind intervals that are compared to OMNI data. Bisector regression analysis reveals that the anti-sunward flow component (Vx) demonstrates exceptional agreement across all missions with near-unity slopes and correlation coefficients of 0.92 for THEMIS and 0.97 for both MMS and Cluster. However, perpendicular velocity components show progressively degraded performance: Vy exhibits correlation coefficients of 0.63-0.77 with intercepts ranging from 21.57 km/s (MMS) to 47.49 km/s (THEMIS), while Vz shows lower correlations (0.42-0.72) with intercepts of 4.73-11.94 km/s. Ion density measurements reveal systematic mission-specific biases: MMS and THEMIS show ion density regression slopes below unity (0.59 and 0.54, respectively), while Cluster shows a slope above unity (1.14) compared to OMNI measurements. Magnetic field measurements show higher consistency, with near-unity slopes and correlation coefficients exceeding 0.84 for Bx and By components. The northward magnetic field component (Bz) exhibits elevated variance ratios and reduced correlations across all missions, reaching as low as 0.74 for THEMIS. These results quantify inherent uncertainties in cross-platform solar wind comparisons and assess the accuracy of time-shifted solar wind measurements in the OMNI database as proxies for near-Earth conditions. Based on the presented statistics, OMNI-equivalent measurements from near-Earth missions can be generated as alternative data sources to support the upcoming SMILE mission, multispacecraft studies, and magnetohydrodynamic simulations that require accurate upstream boundary conditions.
How to cite: Blüthner, G., Volwerk, M., Schmid, D., Nakamura, R., Temmer, M., Roberts, O., Koller, F., and Varsani, A.: Evaluating the OMNI Database: Statistical Analysis of Time-Shifted L1 Data Versus Direct Near-Earth Solar Wind Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9379, https://doi.org/10.5194/egusphere-egu26-9379, 2026.
The May 2024 superstorm (SYM-H peak = –518 nT) was characterized by a three-step main phase, a long and strong recovery phase, and six isolated supersubstorms (SSSs; SML < –2500 nT). We will show that the SSSs were triggered by a strong solar wind driving of ~1017 J. All six SSS events could be explained by both precursor energy and direct driving. The SSS events were unique with highly varied morphology, ranging from an isolated substorm morphology to a storm convection bay scenario. We suggest a two-mode nightside convection electric field to explain the nightside Joule heating variability, and three possible mechanisms for the dayside Joule heating.
References
- Hajra, R., B. T. Tsurutani, G. S. Lakhina, Q. Lu, and A. Du (2024), Interplanetary Causes and Impacts of the 2024 May Superstorm on the Geosphere: An Overview, J. 974, 264 https://doi.org/10.3847/1538-4357/ad7462
- Hajra, R., B. T. Tsurutani, Q. Lu, A. Du, and G. S. Lakhina (2025), Supersubstorms during the May 2024 superstorm, Space Weather Space Clim. 15, 51 https://doi.org/10.1051/swsc/2025047
How to cite: Hajra, R., Tsurutani, B., Lu, Q., Du, A., Lakhina, G., and Narita, Y.: Superstorm, Supersubstorms, and Joule Heating during the May 2024 event: interplanetary triggers, energy budget, and mechanisms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1411, https://doi.org/10.5194/egusphere-egu26-1411, 2026.
In May and October 2024 the aurora was observed at unusually low latitudes across Europe during intervals of significantly enhanced geomagnetic activity in response to the arrival of multiple Interplanetary Coronal Mass Ejections (ICMEs). These storms were two of the biggest storms in Solar Cycle 25 so far. We examine the global magnetospheric response during these intervals using in-situ solar wind and magnetospheric field-aligned current observations. Our analysis suggests that these geomagnetic storms were so large that the magnetospheric activity saturated and could not increase further. We extend our analysis to include large storms from solar cycles 23 – 25 to statistically compare the geomagnetic response to intense storms. We also contrast this against the geomagnetic response to weak and moderate storms.
How to cite: Mooney, M., Milan, S., Nitti, S., Bisi, M., Jackson, D., Forte, B., Henley, E., Gonzi, S., Kinsler, P., Lu, T., Barnes, D., Chang, O., Wild, M., Fallows, R., Jackson, B., and Odstrcil, D.: Characterising the Global Magnetospheric Response to Major ICME Events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10070, https://doi.org/10.5194/egusphere-egu26-10070, 2026.
During the intense storm of December 19, 2015, we benefited from an exceptional configuration of several space missions (MMS, THEMIS, GOES, RBSP) in the inner magnetosphere from the dayside magnetopause to 13 Earth’s radii in the geomagnetic tail . The observations are satisfactory fitted by the simple Tsyganenko model T96. We use it to compute the pattern of closed drift shells of equatorial energetic particles. This pattern shows a strong compression during the Storm Sudden Commencement (SSC) and an increase of total magnetic flux content of about 120 MWb relative to the quiet phase before the storm. Conversely, during the main phase and the first recovery day, we find a decrease by about -800 MWb which could be caused by the effect of cross-tail currents in the plasma sheet on the nightside. These orders of magnitude demonstrate that inner magnetosphere plays an important role in the magnetic flux transport in response to solar wind events.
How to cite: Alqeeq, S., Fontaine, ., Le Contel, O., Akhavan-Tafti, M., Cazzola, E., Atilaw, T., Bourdarie, S., and Maget, V.: Variations of the magnetic flux content in the innermagnetosphere during an intense storm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5466, https://doi.org/10.5194/egusphere-egu26-5466, 2026.
During periods of low clock angle interplanetary magnetic field (IMF), where θ = atan(BY/BZ) ≈ 0, dual-lobe magnetic reconnection (DLR) closes the open magnetospheric flux at the magnetotail lobes, tailward of the cusps. This process results in the reversal of the ionospheric twin-cell convection system and a contraction of the open/closed field line boundary, which, if sustained for a prolonged period, can lead to a fully closed magnetosphere. DLR is also the proposed generation mechanism for Horse-Collar Aurora (HCA), an auroral formation consisting of two cusp aligned arcs that close across the polar cap, accompanied by a 'web' of smaller cusp-aligned arcs (CAAs) equatorward of the main two. We study how different IMF parameters influence the rate at which the open polar cap flux closes, using this as a proxy for the DLR rate, and compare this to MHD models.
We measured the HCA arc velocity and polar cap flux depletion rates using observations from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) on board the Defense Meteorological Satellite Program (DMSP), which provides auroral spectral and positional data. HCA arc velocity was found to increase with higher IMF BZ magnitudes, with no correlation found for solar wind flow speed or density. The open flux depletion rate was also found to increase with increasing IMF BYZ. Coupling functions were also fitted to the arc velocity and open flux depletion rate data, with Pearson r values of 0.58 and 0.52 respectively.
For comparison, 27 magnetohydrodynamic (MHD) models were also run on the NASA Community Coordinated Modeling Center using a range of idealized solar wind conditions. In the models, both IMF BZ and clock angle have a linear correlation with the open flux depletion rate. Solar wind speed also resulted in an increased flux closure rate, contrary to our observational results. No dependence on solar wind density was found. A coupling function was also fitted to the model’s data, resulting in a VSW1.6 solar wind speed dependence, a BYZ0.52 IMF dependence, and a cos3.98(θ/2) clock angle dependence. A number of the MHD simulations also showed extended magnetotails during NBZ, with some extending to over -200RE down-tail.
How to cite: Kennedy, G., Milan, S., Bower, G., Imber, S., and Mooney, M.: Solar Wind Influence on Dual-Lobe Reconnection and Horse-Collar Aurora, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19516, https://doi.org/10.5194/egusphere-egu26-19516, 2026.
Auroral electrojet (AE) activity is a widely used system-level indicator of how the magnetosphere-ionosphere system responds to solar wind driving across a wide range of spatial and temporal scales. While large-scale solar wind parameters are known to control overall levels of geomagnetic activity, auroral responses often show substantial variability under similar upstream conditions. This suggests that additional aspects of solar wind variability, beyond mean magnetic field and plasma properties, may influence how energy and momentum are transferred into the coupled system. In particular, the role of multiscale solar wind turbulence and structured variability in modulating auroral activity remains incompletely understood.
In this work, we examine how multiscale solar wind turbulence contributes to auroral variability using an interpretable machine learning approach. OMNI observations are combined with AE index measurements to construct models that integrate conventional bulk drivers with measures describing solar wind variability across multiple timescales. Interpretable diagnostics are then used to assess how turbulence-related information influences auroral responses under different upstream conditions. While the overall improvement in forecasting skill obtained by including turbulence measures is modest, the results reveal consistent and scale-dependent contributions associated with structured solar wind variability. These findings suggest that solar wind turbulence plays a secondary but informative role in shaping auroral activity, providing insight into how mesoscale variability can modulate system-level coupling and highlighting the value of interpretable machine learning for advancing both physical understanding and space weather prediction.
How to cite: Waters, C. and Chen, C.: Multiscale Turbulence Effects on Solar Wind-Driven Auroral Activity Revealed by Interpretable Machine Learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7502, https://doi.org/10.5194/egusphere-egu26-7502, 2026.
Earth is surrounded by two highly dynamic concentric belts of particle radiation. The outer radiation belt exhibits coherent variability at solar-cycle, seasonal, and 27-day (Carrington) time scales. While the solar-cycle and Carrington variations have been attributed to the recurrence of coronal hole solar wind, the seasonal variation has long been explained by local geometric effects that modulate the solar wind-magnetosphere coupling. Here, we challenge this paradigm by showing that the periodic recurrence of coronal hole solar wind likewise drives the seasonal variation. We further demonstrate that the Alfvénic nature of this solar wind is responsible for the observed electron flux enhancement in the outer radiation belt. These findings provide a unifying framework linking solar magnetic topology, solar wind properties, and magnetospheric dynamics across multiple time scales at Earth and beyond.
How to cite: Lalti, A., Rae, J., Watt, C., Yardley, S., and Raptis, S.: Solar Magnetic Configuration Control over Radiation Belt Electrons, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11180, https://doi.org/10.5194/egusphere-egu26-11180, 2026.
The Earth's outer radiation contains plenty of high-energy electrons. These electron populations exhibit high dynamics, with their fluxes varying by several orders of magnitude. The enhancement of these high-energy electrons greatly increases the likelihood of spacecraft malfunction or failure and significantly influences the solar-terrestrial system's energy and mass coupling, highlighting the importance of fully understanding the mechanisms governing these dynamics from both theoretical and practical perspectives. The plasmasphere is a region usually associated with high-energy electron loss. Using Van Allen Probes measurements, we have found rapid, multi-MeV electron enhancements deep inside the plasmasphere (RMEEIP) that developed within hours at low L-shells, which is distinct from the prompt shock-induced enhancement. Furthermore, we demonstrate that RMEEIP evens are closely associated with the penetration of intense convection electric field inside plasmasphere (PCEF) induced by the high-speed solar wind. This study provides direct evidence that RMEEIP are closely connected to PCEF. The research results are helpful for deepening the understanding of the formation and evolution of high-energy electrons in the radiation belt.
How to cite: Yang, X., Dai, L., Wang, X., and Wang, C.: Multi-MeV electron enhancements deep inside the plasmasphere associated with elevated convection electric field, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11630, https://doi.org/10.5194/egusphere-egu26-11630, 2026.
Transfers of energy and momentum through the Sun–Earth system, including during geomagnetic storms, alter the fundamental state of the magnetosphere. However, previous observations have been limited by the restricted and often single-point nature of in-situ satellite measurements and ground-based observations. The Solar Wind Charge Exchange (SWCX) mechanism, where X-ray emissions are generated through interactions between heavy, highly charged solar wind ions and neutral atoms, offers new opportunities to observe the magnetosphere in a more dynamic and spatially resolved way.
In the presentation, we showcase results that model and analyze SWCX signatures from Earth’s magnetopause and cusp regions using global Magnetohydrodynamics (MHD) simulations enhanced to incorporate heavy ions and X-ray emissions. We also present comparisons between predictions from the global MHD model and those from our embedded kinetic test-particle model. The SWCX mechanism is highly species dependent, governed by interaction cross sections and solar wind ion abundances. Our simulations capture these species-specific properties, producing X-ray emission spectra with species-level resolution.
These emission profiles help us study solar wind drivers, their spatial and temporal evolution, and their ability to distinguish key magnetospheric regions. These findings are highly relevant, for upcoming missions such as SMILE (Solar wind Magnetosphere-Ionosphere Link Explorer), the first mission dedicated to observing global X-ray emissions from Earth’s magnetosphere. The model also enables investigation of kinetic particle effects such as Kelvin–Helmholtz waves and Flux Transfer Events (FTEs), which are discussed further.
How to cite: Kozhikottuparambil Ramachandran, A. and Desai, R.: Spectral properties of SWCX emission from the Earth's outer boundaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1265, https://doi.org/10.5194/egusphere-egu26-1265, 2026.
Interplanetary shocks cause dayside auroras and can cause nighttime substorms. Both phenomena occur within minutes of the shock impingement onto the magnetosphere. The nightside substorms occur if there is solar wind energy preloading within ~3 hrs prior to shock impingement. If there is no energy preloading, a substorm will not occur. There will only be the dayside aurora. In one shock-substorm examined (GRL 2025) the auroral onset occurred at L ~6, indicating that magnetic reconnection was not the mechanism for substorm onset. Possible specific trigger mechanisms will be discussed.
GRL, 26, 8, 1097, 1999; GRL 106, A9, 18957, 2001; Surv. Geo., 22, 101, 2001; ASR, 31, 4, 1063, 2003; GRL, 52, 2025 https:/doi.org/10.1029/2025GL115509.
How to cite: Tsurutani, B., Narita, Y., and Hajra, R.: Shock Dayside Auroras and Shock-Substorms: Internal Magnetospheric Shocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1430, https://doi.org/10.5194/egusphere-egu26-1430, 2026.
Diffuse auroral patches on the dayside are considered as signatures of magnetospheric compressions. However, whether and how these signatures of the diffuse aurora patches are modulated by the upstream sources have not been statistically investigated in previous studies. In this study, we identified 51 dayside diffuse auroral patches and examined their two-dimensional evolutions by using the Time History of Events and Macroscale Interactions during Substorms probes and the ground-based all-sky imager at the South Pole. Two typical events show diffuse auroral patches associated with upstream dynamic pressure enhancements of the bow shock and magnetospheric compressions, followed by their east-west propagations. The statistical results suggest that most conjunction events were associated with foreshock activities, while the remaining events were associated with dynamic pressure enhancements in the pristine solar wind. These azimuthal motions can be either eastward or westward, with initial locations at ∼12-13 and ∼9-10 Magnetic Local Time, respectively, exhibiting a dawn-dusk asymmetry. Additionally, poleward motions were found in all events. Larger dynamic pressure enhancements correspond to faster poleward motions and could push the initial diffuse auroral brightening toward lower latitudes. These characteristics of their poleward motions were consistent with the Tamao path.
How to cite: Wang, B., Xu, X., Nishimura, Y., Ebihara, Y., and Zhi, Y.: Diffuse Auroral Patches induced by Upstream Dynamic Pressure Enhancements of the Bow Shock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8936, https://doi.org/10.5194/egusphere-egu26-8936, 2026.
The polar cusps are a key region of magnetospheric research due to their role in coupling the solar wind and magnetosphere via dayside reconnection. However, discrepancies persist between the spatial extent of the in situ magnetospheric cusp measured by spacecraft and the ionospheric cusp footprint inferred from ground-based observations. Ground-based signatures of reconnection, such as pulsed ionospheric flows (PIFs) and their optical counterparts, poleward-moving auroral forms (PMAFs), commonly span several hours in magnetic local time (MLT), whereas statistical determinations of the cusp extent from in situ observations typically indicate an extent of 1-2 hours of MLT.
We present an event study of cusp extent on 16 December 2017, during which the Cluster spacecraft made a dusk-dawn pass through the northern cusp, while the EISCAT Svalbard Radar operated in a conjugate measurement campaign. This configuration enabled simultaneous ground- and space-based observations of the northern cusp, effectively ‘pinching’ the cusp between a dusk-sector ground-based measurement and a dawn-sector in situ measurement. These observations are supplemented with optical data from all-sky imagers and ionospheric convection data from SuperDARN radars. While individual observations from each instrument are consistent with literature values of 2–4 h MLT, the instantaneous conjugate measurements reveal significantly wider cusp extents of 4.6 h and 5.4 h MLT. Over the duration of the event, the combined observations span 7.2 h MLT, based on measurements separated by 57 minutes, representing an unusually large cusp extent under non-storm solar wind conditions.
Although cusp dynamics are highly variable and responsive to changes in the solar wind, the observed behaviour in this event does not fully account for the anomalously large extent. Instead, these results suggest that conjugate, instantaneous measurements can reveal broader cusp structures or discontinuities that may be underestimated or go unnoticed by single-point or time-averaged observations.
How to cite: Ball, F., Fear, R. C., Herlingshaw, K., and Clausen, L.: Multi-Instrument Ground–Space Conjugate Observations of the Northern Magnetospheric Cusp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13348, https://doi.org/10.5194/egusphere-egu26-13348, 2026.
The cusp region plays a crucial role in the interaction between the solar wind and the Earth's magnetosphere, where solar wind particles can enter the magnetosphere directly. This study first reports that the cusp boundary exhibits a twisting structure, which intensifies with increasing altitude, as demonstrated by global magnetohydrodynamic (MHD) simulations. It is further revealed that the dawn-dusk component of the interplanetary magnetic field (IMF) significantly influences the degree of cusp twisting. This effect can be attributed to the tilt of the magnetic reconnection X-line and the subsequent tilt of the plasma flow directions, modulated by the IMF BY. Moreover, the relationship between the cusp twisting deformations at different altitudes and the magnitude of the IMF BY is quantitatively analyzed across the entire cusp region based on systematic MHD simulation runs. A remarkable enhancement in the twisting angle is indicated with increasing IMF BY and altitude, varying from 0° to 7.6°. The orientation of the cusp twisting follows that of the magnetotail and current sheet dynamics reported in previous studies, implying that the cusp twisting reported here is an essential part of the global effect of non-zero IMF BY on the dayside magnetopause.
How to cite: Gong, Y., Sun, T., Escoubet, C.-P., and Wang, C.: The Effects of IMF BY on the Twisting of Cusp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3765, https://doi.org/10.5194/egusphere-egu26-3765, 2026.
The wave processes which occur during the late growth phase of terrestrial substorms appear to provide a powerful diagnostic for the processes which may lead to the destabilization of the magnetotail and hence to substorm expansion phase onset. Here we review new theory which highlights the potential role of pressure anisotropic ballooning modes as a trigger for substorm onset. In this theory, the expansion of the magnetotail naturally generates parallel pressure anisoptropy energetic ion distributions which lower the threshold for the growth of ballooning modes – providing a plausible physical explanation for the transition of the tail from a stable to unstable configuration. We further present observational evidence from geosynchronous orbit in support of the model prediction. Finally, we demonstrate the utility of ground-based auroral observations for probing the dynamics of the near-Earth magnetotail. Auroral observations we present here clearly show a repeatable and characteristic sequence of late growth phase dynamics, including arc brightenings, the formation of auroral beads, and auroral vortex development, all of which occur well in advance of fast Earthward flows in the tail. Indeed, it is only during that later activity that auroral breakup and strong Earthward flows, which we associate with magnetic reconnection further down the tail, are observed together with strong magnetic bays on the ground. The sequence of events is consistent with an inside-to-outside model at substorm expansion phase onset, and where the stretched nightside magnetic field is destabilised by a temperature anisotropic shear-flow ballooning instability in the transition region from dipole to tail-like fields in the near-Earth plasma sheet.
How to cite: Mann, I. and Babu, S.: Shear-flow Ballooning, Substorm Onset, and Destablisation of the Stretched Terrestrial Magnetotail: New Evidence and Constraints from Energetic Proton Temperature Anisotropy and Auroral Imaging, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15830, https://doi.org/10.5194/egusphere-egu26-15830, 2026.
There is a long-standing debate on the causes of the semiannual variation of geomagnetic activity. One of the prevailing hypotheses is that the Earth’s dipole tilt angle Ψ modulates the dayside reconnection rate, causing the so-called equinoctial effect. Here we perform the first large-scale statistical study to test this hypothesis. We identified isolated substorms in 2010-2019 and used the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) measurements to determine the open magnetic flux variations and estimates of the dayside reconnection rate during these substorm events. We find no significant Ψ dependence of the dayside reconnection rate, opposing earlier studies. However, we find that during low Ψ (equinoxes) a greater amount of open flux is stored in the tail prior to the expansion phase. This suggests that a different mechanism, operating in the magnetotail, contributes to the equinoctial effect and the semiannual variation of geomagnetic activity.
How to cite: Nair, A., Holappa, L., Vanhamäki, H., and Milan, S.: Evolution of open magnetic flux during substorms: the effects of dipole tilt angle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1928, https://doi.org/10.5194/egusphere-egu26-1928, 2026.
There is significant interest within the space physics community in determining if electromagnetic perturbations are Alfvénic in nature. And further, determining if these perturbations are such that they can maintain an electric field parallel to the ambient background magnetic field, as this has important implications for particle acceleration and aurora. The usual approach to determining the nature of the perturbations is to assess the ratio of the electric to magnetic field. If this ratio is given by the local Alfvén speed, then the perturbations are assumed to be Alfvénic. In general, however, the ionospheric height-integrated Pedersen conductivity does not match the equivalent Alfvén wave conductivity (1/μ0VA where VA is the Alfvén speed), and the waves are partially reflected. Immediately above the ionosphere the electromagnetic fields are given by the sum of the incident and reflected waves. Based on Snell’s law the electric to magnetic field ratio is consequently given by 1/μ0ΣP, where ΣP is the height-integrated Pedersen conductivity. As a rough approximation the “near-field” region, where the field ratio is dependent on the Pedersen conductivity, is quarter of a wavelength. Because of this, low frequency Alfvén waves may instead be identified as quasi-static fields. Data from the low altitude TRACERS spacecraft will be used to demonstrate the frequency dependence of the transition from apparently quasi-static structures to Alfvénic.
How to cite: Strangeway, R. J., Cao, H., Bonnell, J. W., Roglans, R., Shen, Y., Wu, J., and Miles, D. M.: Ambiguity in Determining if Electromagnetic Perturbations Observed at Low Altitudes are Alfvénic or Quasi-static, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16176, https://doi.org/10.5194/egusphere-egu26-16176, 2026.
We report coordinated observations of structured, discontinuous energetic electron precipitation (EEP) near the outer radiation belt boundary (oRB), using FY-3E particle measurements together with DMSP/SSUSI auroral imaging and DMSP particle data. These events are characterized by latitudinally separated precipitations with nearly isotropic pitch-angle distributions (PAD) for electrons up to tens–hundreds of keV, and spatial coincidence between EEP and localized auroral structures (double ovals, transpolar arcs, structured diffuse aurora, etc.). Two principal scattering pathways for energetic electron precipitations are identified: (a) field-line curvature scattering (FLCS) in the locally stretched plasma sheet (PS), which produces isotropic precipitations poleward of the oRB; and (b) wave-particle interaction (WPI), where whistler waves scatter electrons across a broad energy range. Furthermore, energetic precipitations are likely confined to closed field lines, indicating the closed field line topology for coexisting auroral structures in polar cap regions. In a discrete arc event, the flux-energy profiles of FY electrons are distinct from the monoenergetic auroral electrons, pointing to a scenario involving different electron precipitating mechanisms: localized structures with shear flows in the equatorial plane create curvature conditions for scattering energetic PS electrons, while the shear flow associated field-aligned currents generate parallel potential in the low-altitude aurora zone, accelerating and precipitating auroral electrons. In an overall diffuse event, the diffuse flux-energy profiles extend from auroral to FY energies, suggesting broadband scattering by waves; additional monoenergetic electrons are superposed on the diffuse spectrum, producing discrete auroral filaments on the diffuse background. The observations of discontinuous correlating energetic and auroral electron precipitations reveals the meso-scale magnetosphere-ionosphere coupling along field lines, and such coordinated examinations can potentially serve as a method to study the coupling processes.
How to cite: Chang, H.-C., Wang, S., Sun, Y.-X., Wang, B.-Y., Cai, L., Yue, C., Zong, Q.-G., Xiao, Z.-Z., Zhou, X.-Z., Zou, H., Ye, Y.-G., and Liu, Y.: Correlated Discontinuous Energetic and Auroral Electron Precipitations in the Polar Cap, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9558, https://doi.org/10.5194/egusphere-egu26-9558, 2026.
The Nightside Transition Region (NTR)—the boundary between the outer and inner magnetosphere—plays a critical role in magnetospheric plasma dynamics. During quiet periods, it acts as a “magnetic wall,” while in active times, it becomes a site of intense plasma energization. Although the large-scale morphology of the NTR is fairly well characterized, the role of mesoscale structures within this region remains poorly understood.
Giant undulations—auroral features located at the equatorward edge of the diffuse aurora—offer a unique opportunity to probe mesoscale dynamics in the NTR. Historically, their formation and evolution have been examined using global auroral imaging, which is limited in both spatial and temporal resolution.
In this study, we leverage recent advancements in ground-based optical instrument arrays to analyze the fine-scale characteristics and temporal evolution of giant undulations. Our findings provide new insights into the generation mechanisms of these structures and their contribution to the overall dynamics of the auroral region, offering a fresh perspective on mesoscale processes in the NTR.
How to cite: Gallardo-Lacourt, B., Kepko, L., Spanswick, E., and Donovan, E.: Mesoscale Auroral Dynamics in the Nightside Transition Region: A Ground-Based Study of Giant Undulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21885, https://doi.org/10.5194/egusphere-egu26-21885, 2026.
Magnetic reconnection and plasma instabilities in Earth's magnetotail can lead to dipolarisation fronts (DFs), rapid enhancements of the magnetic field component aligned with Earth's magnetic dipole axis. DFs are often associated with channels of fast plasma flow, and they accelerate particles and transport magnetic flux to the inner magnetosphere. Satellite observations suggest that DFs propagate Earthward until they decelerate and either vanish, rebound or deflect as they reach the transition region between tail-like and dipole-like magnetic field configurations.
We study the evolution and characteristics of DFs in a global magnetospheric simulation conducted using Vlasiator, a 3D hybrid-Vlasov code that solves ion dynamics by evolving the ion distribution functions explicitly. Events are identified using a magnetic field time derivative threshold, and individual fronts are tracked from their formation to their termination. Preliminary results show how magnetic forces affect the propagation of DFs and how energy is converted as the fronts develop. Tracking the evolution of DFs in global simulations offers a complementary point of view to satellite observations, where following individual fronts is often impossible.
How to cite: Pänkäläinen, L., Cozzani, G., Zaitsev, I., Battarbee, M., Alho, M., Ganse, U., Suni, J., Pfau-Kempf, Y., and Palmroth, M.: Evolution of dipolarisation fronts in a 3D global hybrid-Vlasov simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5567, https://doi.org/10.5194/egusphere-egu26-5567, 2026.
Orals: Thu, 7 May, 08:30–10:10 | Room D2
Disturbances to the magnetopause location driven by upstream pressure variations or flow shear instabilities may be described as surface waves, which act as localised sources of field-aligned currents coupling the magnetosphere to the ionosphere. While global simulations provide semi-quantitative predictions of their large-scale signatures on the ionosphere and ground and, more generally, qualitative features for interpreting observations, how to scale these predictions across the broad possible ranges of wave and system properties are poorly understood. We, therefore, develop a simple numerical model for dispersionless mesoscale magnetopause surface waves within the coupled magnetosphere–ionosphere–ground system to assess possible scaling relations.
In general, the impacts of finite wave packets can be decomposed into periodic fluctuations (with matching wavelength to that in the magnetosphere) along with slowly-varying trends that result from finite wave effects. Finite wave packets act in the far-field like a string of alternating field-aligned currents well described both in the ionosphere and on the ground as a two-dimensional current dipole. In the ionosphere, near-field periodic fluctuations exponentially decay latitudinally away from the open–closed boundary over the reduced wavelength, which may limit how well they can be resolved by radar.
The relationship between the magnetic field above and below the ionosphere becomes more complicated for surface waves than infinite plane Alfvén waves due to the additional spatial structure, which introduces interference across the spectrum of wavenumbers present. This modifies how the ionosphere screens, rotates, and spatially smears magnetic field perturbations across all three components in different ways, importantly resulting in latitudinal scales of amplitude and polarisation variation smaller than typical ground magnetometer spacings, motivating the need for denser networks. A range of effective skin depths in the ground are applicable to surface waves, meaning ground induction can vary between a near-perfect insulator to a good conductor, affecting both observable ground magnetic fields and resulting geoelectric fields. The predicted peak amplitudes of surface waves' impacts suggest they may act as significant sources of ionospheric/thermospheric Joule heating and geoelectric fields in the ground, thereby contributing to space weather impacts though highly localised latitudinally.
Our results provide key predictions for interpreting ground-based observations, of particular timeliness with the rollout of new digital ionospheric radars and the upcoming SMILE mission's planned conjugate ground–space campaigns.
How to cite: Archer, M., Heyns, M., and Southwood, D.: Characterising mesoscale magnetopause surface waves within magnetosphere–ionosphere–ground coupling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17158, https://doi.org/10.5194/egusphere-egu26-17158, 2026.
The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is an ESA–CAS joint mission aiming to provide the first global soft X-ray images of the dayside magnetosphere through observations of solar wind charge exchange (SWCX) emission. A key objective of SMILE is to continuously monitor large-scale magnetospheric boundaries, such as the magnetopause, under varying solar wind conditions using the Soft X-ray Imager (SXI). The SMILE Modeling Working Group (MWG) coordinates a range of activities aimed at supporting the scientific exploitation of SXI observations. These include, among others, the generation of simulated data products that are representative of those expected from the SXI processing pipeline, as well as the development and testing of analysis strategies for boundary identification. The simulations are based on emissivity cubes derived from global simulation models and incorporate instrumental effects such as background components and vignetting. As part of this effort, a community-wide analysis exercise, named the SMILE SXI Grand Analysis Challenge (GAC), has been initiated using a single-orbit SXI simulation with one-minute temporal resolution. The aim is to assess the capability of different analysis techniques to extract the time-dependent location of the magnetopause from simulated SXI images and to evaluate the suitability of the current data products for this purpose. The status and preliminary outcomes of the MWG activities, including the GAC, will be presented.
How to cite: Sun, T., Connor, H., Samsonov, A., Sembay, S., and Carter, J.: Progress of the SMILE Modeling Working Group , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15974, https://doi.org/10.5194/egusphere-egu26-15974, 2026.
Injections of energetic ions into the inner magnetosphere constitute one of the main sources of ring current enhancement during geomagnetic storm main phases, especially for energies in the range of 10~200keV. So far, the majority of investigations on energetic ion injections were performed at L>4.0 in the inner magnetosphere, while the study of ion injections in L<4.0 regions is relatively scarce. In this paper we have developed a method to identify ion injections for L<4.0 based on energetic ion fluxes vs L profiles during geomagnetic quiet times. We have selected 120 ion injections with 15 isolated injections and 105 storm-time injections based on the flux ratios between active and quiet periods. Energetic ions can be seldom injected into L<3.0 during isolated substorms, while they can reach much deeper orbits during storm-time. Additionally, we have calculated the correlation coefficients between the adjacent orbits during the geomagnetic active and quiet times in the same orbit categories. The results show that energetic ions with 150~750keV are hardly injected into L<4.0 for both ascending and descending periods. In contrast, lower energy ions with 50keV<E<150keV are injected into L<4.0 during geomagnetic storm-times, with deepest injection depth at L=2.4.
How to cite: He, Z., Dai, L., Duan, S., Roth, I., and Wang, C.: How deeply do the energetic particles inject into the inner magnetosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4667, https://doi.org/10.5194/egusphere-egu26-4667, 2026.
We report the first observation of the plasmasphere's periodic response to solar wind high-speed streams (HSS) during the declining phase of Solar Cycle 23, based on plasmapause location data from the IMAGE and THEMIS satellites. In both 2005 and 2008, the daily variability of the plasmapause exhibits a strong anti-correlation with solar wind speed, oscillating coherently at specific timescales. A similar anti-correlated variation is identified in the latitude of the midlatitude ionospheric trough (MIT) minimum, derived from electron density measurements by the DMSP F16 satellite. Periodogram analysis reveals a distinct 9-day periodicity in 2005, and both 9- and 13.5-day periodicities in 2008 across all parameters. These findings provide direct evidence of magnetospheric modulation by recurring solar wind drivers and establish a clear connection between the plasmasphere and the midlatitude ionosphere under periodic solar forcing.
How to cite: Li, Q.-H., He, M., Hao, Y.-Q., He, F., and Zhang, X.-X.: Periodic Response of Plasmasphere to Solar Wind High-Speed Streams, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4884, https://doi.org/10.5194/egusphere-egu26-4884, 2026.
Geomagnetic storms are well-known disturbances of the Earth’s magnetic field associated with extreme solar events. Studies of geomagnetic storms are of interest for numerous scientific and societal reasons as they can strongly alter the Earth’s magnetosphere, the near-Earth geomagnetic field, the ionosphere-thermosphere and the lower atmosphere environments, and the electromagnetic environment below and close to the Earth’s surface due to induction of electric currents in the solid Earth. A key to furthering our understanding of the impact of geomagnetic storms is to better characterize the coupling between the Earth’s magnetic field and the solar wind, which takes place through the electric current system that connects the Earth’s magnetosphere to the high-latitude ionosphere.
F-region field-aligned and E-region toroidal ionospheric currents play an important part in magnetosphere-ionosphere coupling, and often need to be studied jointly. This can be done using the network of ground vector magnetic measurements, complemented by vector satellite observations at LEO satellite altitudes. Unambiguously interpreting the highly dynamic and spatially complex ionospheric signals in these data, however, is a challenging task, as these measurements include contributions from all other natural sources, and because they only provide incomplete space-time data coverage. One approach to extract the ionospheric signal and synthesize information from several data sources is to construct empirical models. Representing both storm-time E- and F-region ionospheric currents at the appropriate cadence in such models, however, generally requires solving severely underdetermined inverse problems, which can hardly be done robustly given the relatively sparse coverage of modern geomagnetic data.
We present a new scheme that specifically tackles this issue. It allows to construct fully three-dimensional empirical models of high-latitude E- and F-region ionospheric electric currents and magnetic fields during geomagnetic storms at periodicities down to one minute. The main idea is to reduce the model parameter space by relying on optimized basis functions of space, derived from a set of 5 numerical simulations of the TIEGCM first principle physics model, and optimized basis functions of time, directly derived from ground magnetic observations. We constructed a first model of the high-latitude ionosphere in the Northern hemisphere constrained by ground and magnetic perturbation data from the Iridium satellite constellation for the storm of May 2017. The model shows excellent agreement with an independent TIEGCM numerical simulation of this same storm, as well as with independent data from the Swarm, CryoSat-2, and GRACE satellites.
How to cite: Fillion, M., Alken, P., Egbert, G., Maute, A., Lu, G., and Pham, K.: Rapid dynamics empirical modeling of high-latitude three-dimensional ionospheric electric currents during geomagnetic storms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9519, https://doi.org/10.5194/egusphere-egu26-9519, 2026.
The question of interest in this study is: Given the external driving of monochromatic MHD fast mode waves into the magnetosphere, what determines the location and polarization of (fundamental mode) field line resonances (FLRs), in the general case of a non-axisymmetric Alfvén speed and magnetic field topology? This is of particular interest for considering the role of FLRs, or Shear Alfvén Wave (SAW) eigenfunctions, in radiation belt and ring current particle energization, transport and loss by resonant wave-particle interactions, since the efficiency of coupling is dependent on the SAW polarization.
In particular, we seek to determine whether or not the SAW polarization direction in externally driven FLRs remains constant as a function of position along a given field line with respect to neighbouring field lines, as has been assumed in previous studies. In addressing this question we seek to extend and unify the works of: a) Wright et al., (Astrophys. J., 2016, J. Geophys. Res. 2022), which considered the case of a non-axisymmetric Alfvén speed in a dipole and compressed dipole magnetic fields (making the above assumption); and b) Rankin et al. (Adv. Space Res., 2006) and Kabin et al., (Ann. Geophys., 2007), which considered an arbitrary magnetic geometry, but made no constraints SAW polarization.
A new formulation based on vector Sturm Liouville theory for driven SAW eigenfunctions in the Resonant Zone (Wright et al., 2016) is proposed, in which the unconstrained vector eigenfunctions of Kabin et al. (2007) form a complete basis under background conditions without field-aligned currents (FACs). Based on the results of our coupled 3D MHD model for ULF waves, we show that only a very limited number of these eigenfunctions are required to represent the MHD waves in the vicinity of an FLR with reasonable accuracy. Using this as an assumption, we can find solutions for fundamental mode SAWs within the Resonant Zone (described as a linear combination of these basis functions) with eigenfrequencies that match an external driving frequency – essentially producing resonance maps for FLRs similar to those of Wright et al (2016), but without any assumption on the polarization. We further generalize our approach by considering the additional effect of the addition of background FACs on the SAW eigenfunction solutions. In this case the vector ODE equation for SAWs is no longer self-adjoint, however we show that a basis can still be defined by a biorthogonality condition using the adjoint differential operator. This allows a similar spectral method to calculate resonance maps for a given driving frequency.
How to cite: Degeling, A., Rankin, R., Kabin, K., Waters, C., and Wright, A.: Driven Field Line Resonance Polarization in a General Magnetospheric Geometry , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20385, https://doi.org/10.5194/egusphere-egu26-20385, 2026.
Ultra low frequency (ULF) waves occur in the Earth’s magnetosphere due to various drivers. For example, large-scale structures originating from the Sun, such as high-speed streams (HSS) and interplanetary coronal mass ejections (ICME), are associated with elevated wave activity. ULF waves, especially the Pc5 frequency range (2-7 mHz), cause electron acceleration in the radiation belts. These high-energy electrons can damage satellites in orbits near the radiation belts. This is one of the main motivations of researching why and when ULF wave activity occurs.
In this work we define a “wave storm” to describe time periods of higher Pc5 wave power, by using a Pc5 index calculated from ground-based magnetometer measurements from the Earth's dayside. We investigate which structures drive the most wave activity and which cause the most intense wave storms. The number of wave storms is observed to have variation along the solar cycle. Similarly to geomagnetic storms, ICMEs drive the majority of the most intense wave storms. Sheath regions on ICMEs increase the probability of a wave storm. We compare the values of solar wind parameters during and outside of wave storms. The clearest differences are found in solar wind velocity, as expected. To investigate the effect on radiation belts, we do a similar comparison to geostationary electron flux indices. Radiation belt electron flux is observed to increase in relation to wave storms, but with a time lag.
How to cite: Ojuva, M., Turc, L., Lipsanen, V., Hoilijoki, S., Osmane, A., Dahani, S., Kalliokoski, M., Tao, S., and Kilpua, E.: Pc5 wave storms in near-Earth space, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11251, https://doi.org/10.5194/egusphere-egu26-11251, 2026.
We present a comprehensive methodology for Kp index calculation based on the PPMLR(Piecewise Parabolic Method with Linear Reconstruction) global MHD simulation model, which simulates Earth's dynamics in the solar wind-magnetosphere-ionosphere interaction system. The Kp index is a widely used geomagnetic activity indicator crucial for space weather monitoring and forecasting. Accurate understanding and prediction of geomagnetic activity levels are essential for space weather operational services, satellite operations, and power grid management. Global MHD simulations provide a physics-based approach to model ground magnetic disturbances driven by the complex Earth's magnetospheric system under varying solar wind conditions. In this work, we first conduct a comprehensive validation of the PPMLR-MHD model by comparing simulated magnetic disturbances with observational data from SuperMAG ground-based magnetometer stations distributed across both hemispheres. The model successfully reproduces the spatial and temporal variations of geomagnetic disturbances during different geomagnetic activity levels, including quiet periods and storm events. This validation confirms the capability of this global magnetohydrodynamic model to capture the physical processes of the coupled system. Subsequently, we apply a normalization method to the model-generated global ground magnetic disturbances at the standard station locations provided by ISGI (International Service of Geomagnetic Indices). A weighted averaging procedure based on longitudinal distribution is then employed to derive unique global Kp index values for each three-hour interval, following the standard Kp determination methodology. Detailed comparison with observed Kp indices demonstrates that our methodology successfully captures both the trends and magnitudes of Kp variations throughout different phases of geomagnetic activity, indicating significant potential for operational space weather forecasting based on global magnetospheric simulations.
How to cite: Xi, X., Guo, X., Wang, C., and Wang, D.: Kp Index Simulation Based on Global MHD Modelof Earth's Magnetosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20470, https://doi.org/10.5194/egusphere-egu26-20470, 2026.
Strong Thermal Emission Velocity Enhancement (STEVE) events are bright mauve optical emissions that periodically occur around magnetic midnight in sub-auroral regions often after a substorm onset. Substorms are known to generate STEVE events but the vast majority of substorms are not associated with STEVE emissions. In this study we will discuss:
1) For STEVE events, what is the temporal response of the ionosphere (electron density, ion and electron temperature, ion velocity) and the spectral response after substorm onset?
2) What are the conditions of the magnetosphere-ionosphere system prior to a STEVE event; can preconditioning be identified?
3) How are the mesoscale flow patterns associated with STEVE events different from those associated with substorm events in general?
A novel and compelling component of this research is the incorporation of Incoherent Scatter Radar (ISR) data using the Poker Flat ISR (PFISR), all-sky imager data (namely from THEMIS), as well as citizen science lists of STEVE sightings. We aim to characterize the plasma signatures of STEVE and STEVE-like events (where there is no detectable optical signature but plasma characteristics are consistent with STEVE observations).
Using PFISR data collected from 2010-2025, in combination with spacecraft and magnetometer data, we aim to evaluate the Magnetosphere-Ionosphere coupling properties associated with STEVE events and STEVE-like events. This presentation will discuss these findings. In addition, we will present preliminary findings of amplitude and phase power spectra during STEVE events using high rate GNSS receivers at various locations in the Canadian Arctic.
How to cite: Derghazarian, S., Goodwin, L. V., Kc, P., Perry, G. W., and Gallardo-Lacourt, B.: Investigating Ionospheric Signatures and Magnetosphere-Ionosphere Coupling During STEVE and STEVE-like Events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22860, https://doi.org/10.5194/egusphere-egu26-22860, 2026.
The energy transfer and coupling between the solar wind and Earth’s magnetosphere are central issues in geophysics. Solar wind charge exchange (SWCX) generates soft X-ray emissions (0.1–2 keV) through interactions between highly charged solar wind ions and neutral atoms in the terrestrial exosphere, providing a new means to globally observe magnetospheric structures. The Solar wind–Magnetosphere–Ionosphere Link Explorer (SMILE), jointly developed by the Chinese Academy of Sciences (CAS) and the European Space Agency (ESA), will carry the Soft X-ray Imager (SXI) and is scheduled for launch soon. SXI will, for the first time, enable continuous global imaging of key large-scale magnetospheric structures, including the bow shock, magnetopause, and cusps, through multi-angle scanning observations.
Three-dimensional tomographic reconstruction requires multi-angle projection data to invert line-of-sight radiative integrals and recover volumetric emissivity distributions. Unlike conventional surface-based imaging, magnetospheric soft X-ray emissions originate from optically thin volume emission produced by SWCX, and their line-of-sight integration conforms to the Radon transform framework. Each SXI pixel represents the integral of X-ray emissivity along its viewing direction. In principle, three-dimensional emissivity distributions can be reconstructed by solving large linear systems. However, the orbital geometry of SMILE severely limits angular coverage, resulting in sparse projections and a strongly ill-posed inverse problem. In addition, the nominal SXI imaging cadence of approximately 5 minutes limits the ability to resolve rapid magnetospheric dynamics.
To address these challenges, this study proposes a progressive deep-learning-driven framework for high-precision three-dimensional and dynamic magnetospheric reconstruction from limited-angle SXI observations. First, a Deep Sparse Coding Estimation Network (DSCE-Net), combining deep learning with sparse representation theory, is developed to suppress instrumental and background noise, significantly improving signal-to-noise ratio and preserving structural integrity in the X-ray images. Second, to compensate for missing projection data caused by restricted viewing angles, a three-dimensional conditional Generative Adversarial Network (3D-CGAN) incorporating multi-scale feature extraction and magnetospheric physical prior constraints is introduced to generate physically consistent projections, effectively alleviating the ill-posedness of limited-angle tomography. Based on the completed projection set, iterative tomographic algorithms are then applied to reconstruct high-accuracy static three-dimensional emissivity distributions, substantially improving the localization and morphology of key structures such as the bow shock and magnetopause. Furthermore, to overcome temporal resolution limitations, an Adaptive X-ray Dynamic Image Estimator (AXDI-Estimator) is designed to fuse 1-minute OMNI solar wind parameters with low-cadence SXI observations, driving simulations to generate continuous minute-scale X-ray image sequences and enabling dynamic tomographic reconstruction with spatiotemporal consistency.
Numerical validation using MHD and Jorgensen–Sun models demonstrates that the proposed framework significantly outperforms traditional methods in image quality, structural fidelity, and dynamic tracking capability. The subsolar magnetopause standoff distance error is constrained within 0–0.4 Re under nominal conditions and remains below 2.4 Re under extreme solar wind conditions. The results meet SMILE mission requirements for spatial resolution, localization accuracy, and dynamic reconstruction, providing an effective solution for three-dimensional dynamic imaging of space plasmas under limited observational geometries.
How to cite: Wang, R., Sun, T., and Li, D.: A New Neural Network Approach Integrating Prior Knowledge for Dynamic Three-Dimensional Tomographic Reconstruction of the Earth's Magnetosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4738, https://doi.org/10.5194/egusphere-egu26-4738, 2026.
Short large‐amplitude magnetic structures (SLAMS) are common magnetic field structures in the terrestrial foreshock and play an important role in particle dynamics, often leading to the formation of unstable ion and electron velocity distributions. Consequently, the presence of SLAMS can naturally excite plasma waves at various scales. This study integrated MMS observations with instability theories to investigate the local excitation of multi-scale magnetosonic whistler waves associated with SLAMS. The findings revealed that low-frequency magnetosonic whistler waves appear in the tailing region of SLAMS, where solar wind ions and low-energy ions coexist. Within SLAMS, counter-streaming high-frequency magnetosonic whistler waves (also known as whistlers) are characterized by an anisotropic electron temperature, where the perpendicular temperature exceeds the parallel temperature. Based on instability theory analysis, we proposed that the excitation of low-frequency magnetosonic whistler waves results from two-stream instability, driven by the relative drift between low-energy ions and electrons, while the excitation of whistler waves arises from electron temperature anisotropy instability. These results indicated that SLAMS significantly influence (and may even determine) the dynamic properties of particles and the excitation of certain types of plasma waves.
How to cite: Yao, Y.: Multi-scale Magnetosonic Whistler Waves Induced by SLAMS in the Earth's Foreshock, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3700, https://doi.org/10.5194/egusphere-egu26-3700, 2026.
Geostationary Operational Environmental Satellites (GOES) in geostationary orbit (GEO) have previously been utilized for magnetospheric studies using magnetic field data; however, plasma measurements from GOES have received little attention. Since GOES-16, the onboard Magnetospheric Particle Sensors - Low Energy instrument has allowed measurements of ions and electrons in the range from ~30 eV to 30 keV. During extreme solar wind conditions, boundary layers, dayside magnetopause, and even the bow shock may be compressed to GEO, making plasma measurements from GOES valuable for providing energy flux spectra, pitch-angle distributions, and plasma moments at this position, as well as for conjunction observations with other missions. In this study, we present coordinated GOES and THEMIS observations during the 10 May 2024 solar wind event. The energy flux data for both missions are shown. We identify a new structure on the inner side of the magnetopause, which we term a “compression layer”, within which a “three-energy-level” structure is observed. We suggest that both structures are related to pure compression under northward IMF and the plasmaspheric plume. We also show that the bow shock was temporarily compressed to GEO during this event, and we further present additional examples illustrating the application of GOES plasma observations to magnetospheric boundary studies.
How to cite: Li, S., Pi, G., Nemecek, Z., and Safrankova, J.: GOES Plasma Observations Applied to the Magnetospheric Boundary Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4270, https://doi.org/10.5194/egusphere-egu26-4270, 2026.
Omega bands are mesoscale auroral structures that appear as eastward-moving poleward protrusions in the auroral oval. They typically appear in the post-midnight sector during periods of enhanced geomagnetic activity. Omega bands have been associated with Ps6 pulsations and rapidly time-varying magnetic fields on the ground, making them highly relevant to space weather forecasting. However, while the solar wind and magnetospheric drivers of omega bands have been previously studied, the characteristic signatures of omega band substorm events have not been identified.
In this work, we compare solar wind, magnetospheric, and geomagnetic parameters measured during general substorm activity to the same parameters measured during 205 omega band events from 1997 to 2007 identified using the MIRACLE network. Non-omega substorm events are identified using spline fitting techniques to locate positive bays in the SuperMAG lower auroral electrojet index, and filtered to match the omega band substorm events in intensity. We use OMNI data to determine the solar wind drivers of these events and data from GOES and SuperMAG to identify magnetospheric and geomagnetic signatures of these events. This analysis will allow us to identify the unique solar wind drivers and magnetospheric configurations associated with omega band formation and improve our understanding of magnetosphere-ionosphere coupling dynamics during periods of enhanced geomagnetic activity.
How to cite: Cribb, V., Pulkkinen, T., Kepko, L., Gallardo-Lacourt, B., McPherron, R., and Partamies, N.: Unique solar wind and magnetospheric drivers of omega band substorm activity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4286, https://doi.org/10.5194/egusphere-egu26-4286, 2026.
The magnetopause is the key boundary that regulates solar-wind energy and plasma entry into Earth’s magnetosphere. While its responses under southward and northward interplanetary magnetic field (IMF) conditions have been extensively studied, whether a systematic, large-scale magnetopause reconfiguration can occur during radial IMF (IMF nearly aligned with the solar-wind flow) remains unclear. Here we investigate a prolonged (>30 min) radial-IMF interval using coordinated multi-point spacecraft measurements, Antarctic ground-based auroral observations, and a three-dimensional global hybrid simulation. We identify a previously unrecognized large-scale distortion of the dayside magnetopause, characterized by a sunward-protruding bulge coexisting with a cusp-to-cusp valley that extends from the Northern to Southern polar regions and reaches a depth of approximately one Earth radius. Observations indicate that magnetosheath high-speed jets can first produce localized magnetopause indentations and then trigger magnetic reconnection. The associated poleward moving auroral forms (PMAFs) provide independent ionospheric evidence for reconnection-driven flux transfer and dayside magnetosphere erosion. The global hybrid simulation further demonstrates that multiple jets can continuously impact the magnetopause and induce multi-site reconnection, allowing magnetosphere erosion to accumulate and thereby forming large-scale magnetopause valleys consistent with the observations. These results revise the conventional view that magnetosheath jets mainly cause short-lived, localized disturbances, and instead show that under sustained radial IMF they can drive large-scale magnetopause restructuring and enhance solar wind–magnetosphere–ionosphere coupling, with potential implications for space-weather processes
How to cite: Guo, J., Lu, S., Lu, Q., and Wang, B.: Large-scale distortion of the dayside magnetopause under radial interplanetary magnetic field, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4363, https://doi.org/10.5194/egusphere-egu26-4363, 2026.
Following a southward turning of the interplanetary magnetic field (IMF), dayside magnetic reconnection rapidly re-establishes sunward convection on closed field lines, modifying plasma flow near the magnetopause. How magnetopause Kelvin–Helmholtz (KH) vortices develop and inflxuence magnetospheric convection under southward IMF conditions remains unclear. Here, we use global magnetohydrodynamic (MHD) simulations to investigate the formation, evolution, and convection impact of KH vortices under fast (800 km/s) and slow (400 km/s) solar-wind conditions.After the IMF turns southward, KH vortices form along the magnetopause and extend across the low-latitude boundary layer (LLBL) into the closed-field-line convection region, locally distorting the global convection pattern. Regardless of solar-wind speed, the azimuthal region of distorted convection near magnetic local time 06 exhibits a characteristic thickness of approximately 3–4 RE (~3° in magnetic latitude). These vortices and associated convection perturbations propagate antisunward. Compared with slow solar-wind cases, fast solar-wind conditions lead to more rapid earthward propagation and deeper penetration of the distorted convection into the inner magnetosphere. These results demonstrate that inner magnetospheric convection can be shaped by LLBL instabilities in the southward IMF.
How to cite: Wang, K., Dai, L., Zhu, M., Ren, Y., Wang, X., Wang, T., and Wang, C.: Inner Magnetospheric Convection impacted by Magnetopause Kelvin–Helmholtz Vortices Following an IMF Southward Turning: Global MHD Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4691, https://doi.org/10.5194/egusphere-egu26-4691, 2026.
Geomagnetic substorms transfer solar wind energy into the planetary magnetosphere and ionosphere, producing auroral displays and ground magnetic disturbances, particularly intense during the expansion phase. Despite decades of study, the mechanisms governing the expansion phase remain unresolved. Based on coordinated observations of storm-time intense substorms, we reveal that substorm expansion is temporally embedded within a global cycle of field-aligned currents and auroral electrojets, coupled to large-scale plasma convection. The cycle manifests as a coherent movement of current peaks across magnetic longitude and latitude—first antisunward and equatorward, then sunward and poleward—and coincides with enhanced sunward ionospheric convection. The antisunward–equatorward phase, corresponding to intervals of dominant dayside reconnection, begins with a convection-driven DP-2 current and can stepwise transition into a substorm-expansion DP-1 current. During the subsequent sunward–poleward phase, reflecting intervals of dominant nightside reconnection, DP-1 either persists from the earlier interval or develops within this phase. These observations show that expansion onset can occur under dominance of either dayside or nightside reconnection, while the full development of DP-1 generally involves nightside reconnection, offering new insight into substorm evolution—an objective central to the SMILE mission.
How to cite: Dai, L., Wang, T., Escoubet, C. P., Gonzalez, W., Ren, Y., Zhu, M., Wang, S., Wang, C., Wang, X., Wang, K., and Liu, J.: Substorm Expansion Embedded in a Global Cycle of Field-Aligned Currents and Auroral Electrojets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5346, https://doi.org/10.5194/egusphere-egu26-5346, 2026.
The auroral oval, a luminous manifestation of solar wind–magnetosphere interaction, is typically confined to Earth’s polar regions. The geomagnetic superstorm of 10 May 2024, however, provides a clear case in which auroras expanded to extreme low magnetic latitudes. Through an analysis focusing on dusk-side auroras, combined with coordinated observations and magnetohydrodynamic simulations, we demonstrate that the primary cause was an extreme equatorward movement of both field-aligned currents and auroral electrojets. This systemic movement was driven by intense sunward plasma convection penetrating to unusually low latitudes. Specifically, these convection-driven auroral currents shifted equatorward, reaching south of 60° geomagnetic latitude, while the brightest auroral emissions extended to 50°. Furthermore, simulations indicate that a strong negative interplanetary magnetic field‘s y-component compressed the plasma sheet equatorward, which specifically enhanced the southward displacement of the dusk-side auroral oval in the Northern Hemisphere. Our findings establish a convection-driven mechanism for mid-latitude auroras during superstorms, providing a critical basis for forecasting these extreme space weather events.
How to cite: Wang, T., Dai, L., Ren, Y., and Zhu, M.: Low Magnetic Latitude Auroral Oval Through a Convection-Driven Equatorward Shift of Auroral Currents, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6087, https://doi.org/10.5194/egusphere-egu26-6087, 2026.
Enhancements of large-scale convection electric fields in the inner magnetosphere, likely linked to low-latitude penetration electric fields in the ionosphere, are key components of solar wind–magnetosphere ionosphere coupling. These fields reflect large-scale magnetosphere convection induced by the solar wind and are known to influence various geomagnetic indices such as Kp, AU, and Dst. In this study, we examine large-scale electric fields observed by the Van Allen Probes, along with solar wind conditions and geomagnetic indices, during 191 isolated high-speed solar wind events from October 2012 to August 2019. We find that the strength of the electric field within L‐shells less than 5.5 increases with both solar wind speed and the southward component of the interplanetary magnetic field. Superposed epoch analysis reveals that the penetration depth of the convection electric field increases with solar wind speed. When solar wind speed exceeds 550 km/s, significant electric fields reach L ∼ 3. Statistical analyses show that the Kp, AU, and Dst indices exhibit an approximately linear relationship with electric field strength when Ey, RMS<1 mV/m. Above this threshold, these indices exhibit a slower rate of increase, indicating a nonlinear response of geomagnetic indices to stronger convection electric fields. Additionally, AU correlates approximately linearly with Kp, while Kp shows a roughly logarithmic relationship with Dst. These results confirm that magnetospheric convection significantly influences Kp, AU, and Dst, particularly under high-speed solar wind conditions.
How to cite: Wang, X., Dai, L., Wang, T., Ren, Y., Zhu, M., Yang, X., Wang, C., and Gonzalez, W.: Inner magnetospheric convection electric fields and corresponding geomagnetic indices during high-speed solar wind streams, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6117, https://doi.org/10.5194/egusphere-egu26-6117, 2026.
Substorms are often described by a loading–unloading cycle, where onset follows gradual loading of solar wind magnetic flux in the magnetosphere. Yet observations indicate that intense substorms can also be directly driven, though the underlying magnetospheric mechanism is unresolved. Here, combining global observations and simulations of the 10 May 2024 geomagnetic superstorm, we provide evidence that solar-wind–driven magnetospheric convection triggered an intense substorm. At 17:17 UT, a shock-compressed southward interplanetary magnetic field enhanced sunward convection and auroral currents, which rapidly extended to the nightside and initiated substorm expansion within six minutes. Simulations reproduce this response, revealing that dayside-driven convection of closed field lines depleted nightside flux and thinned the current sheet. This lowered the onset threshold and triggered substorm expansion with negligible flux loading. After onset, nightside flux loading became significant as a reconnection X-line formed near 10 Earth radii, extended azimuthally, and supported a global substorm current wedge.
How to cite: Ren, Y., Zhu, M., Dai, L., Gonzalez, W., Wang, S., Wang, C., Escoubet, C., Zhang, J., and Zong, Q.: Evidence for solar-wind triggering of substorm onset during the May 2024 superstorm: coordinated global observations and simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6407, https://doi.org/10.5194/egusphere-egu26-6407, 2026.
Large-scale solar-wind-driven magnetospheric convection governs the formation of global electric currents responsible for geomagnetic activity and indices. Despite its importance for space-weather dynamics, quantitative descriptions of the magnetospheric convection electric field remain limited. Widely used analytical models, such as the Volland--Stern formulation, have not been systematically constrained by in situ observations. Here, we derive closed-form symbolic expressions for the magnetospheric convection electric field directly from Van Allen Probes measurements using PhyE2E, a neural-symbolic regression framework for physics discovery. Without assuming a predefined functional form, PhyE2E decomposes the regression problem using second-order neural derivatives, synthesizes candidate symbolic expressions, and refines them through Monte Carlo tree search and genetic programming. Applied to statistical observations spanning multiple geomagnetic activity levels, the resulting symbolic formulas reproduce the observed convection electric fields with substantially improved accuracy compared with the classical Volland--Stern model. These results provide an explicit, data-driven model of inner-magnetospheric convection electric fields for space-weather studies.
How to cite: Hu, X., Dai, L., Wang, X., Ren, Y., and Wang, T.: Data-driven symbolic expression of magnetosphere convection from Van Allen Probes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6593, https://doi.org/10.5194/egusphere-egu26-6593, 2026.
High-latitude reconnection between the northward IMF and the Earth’s magnetosphere typically involves open lobe magnetic field lines in the polar cap. However, a study of cusp plasma populations reported unusual high-latitude reconnection events featuring closed “nonlobe” magnetic field lines, whose presence at the magnetopause was not explained (Fuselier et al., 2018). Partial/Complete closure of the polar cap has been linked to mechanisms with telltale transpolar auroral arc (TPA) and horse-collar aurora (HCA) signatures, but can these mechanisms explain the observed nonlobe reconnection? We analyse auroral signatures during 12 nonlobe reconnection events identified by Fuselier et al., (2018). Of these, 9 events (75%) exhibit evidence for a TPA or an HCA within two hours of the reconnection time, a rate far exceeding expectation from random sampling (~20%). The result suggests strongly that nonlobe reconnection can be explained by either TPA wedge reconnection (Kaweeyanun et al., 2025) or dual lobe reconnection that produces HCAs (Milan et al., 2020b). If so, cusp plasma observations can be used to detect both types of reconnection, greatly expanding the size of available event samples that will allow further investigations into the phenomena, including calculation of the reconnection rate.
How to cite: Kaweeyanun, N. and Fear, R.: Does high-latitude “nonlobe” reconnection under northward IMF involve closed magnetic field lines linked to polar cap auroras?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7910, https://doi.org/10.5194/egusphere-egu26-7910, 2026.
Understanding the spatio-temporal organization of geomagnetic field variations during intense magnetic storms is essential for characterizing the large-scale response of the magnetosphere–ionosphere system. In this study, we investigate the temporal evolution of geomagnetic field correlations using a network-based approach applied to ground-based observations.
We consider minute-resolution magnetic field data recorded by 50 geomagnetic observatories located in the Northern Hemisphere at magnetic latitudes higher than 40°. The analysis focuses on the temporal behavior of the horizontal component of the geomagnetic field during the intense magnetic storm that occurred in May 2024. A functional network is constructed by quantifying the statistical relationships between pairs of observatories over sliding time windows, allowing the connectivity structure of the network to evolve in time.
The network properties are analyzed using standard metrics from complex network theory with the aim of characterizing changes in the network topology between geomagnetically quiet conditions and storm periods. By comparing the network structure before, during, and after the storm main phase, this study aims to identify collective patterns and large-scale reconfigurations in geomagnetic field dynamics at high latitudes.
This work explores the potential of network analysis as a complementary tool for investigating geomagnetic storms using multi-station ground-based observations, providing insights into the complex/collective behavior of the geomagnetic field variations during extreme space weather events.
This research was funded by the Space It Up! project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0—CUP n. I53D24000060005.
How to cite: Consolini, E., De Michelis, P., and Consolini, G.: Temporal evolution of geomagnetic field disturbance during the May 2024 storm: a network approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8095, https://doi.org/10.5194/egusphere-egu26-8095, 2026.
The characteristics of the southward component of the interplanetary magnetic field (IMF) component in GSM coordinate system, Bs, within 1990--2017 for different solar activity levels are presented. We show that Bs ordered according to the polarity (Bs polarity fields) exhibit a "pair of spectacles" pattern, the two annual sinusoidal-like variations of opposite phase.
It means that Bs polarity fields exist for toward/away field in fall/spring ("unfavorable" seasons). These fields are reduced, but are not zero. Thus, in "unfavorable" seasons, geomagnetic activity can be due to reduced Bs and not because the field is northward pointing.
This study provides a new and deep inside into the pattern of experimental Bs which differs from previous models.
In this way this research contributes in better understanding of the origin of Bs, which is the important IMF component in controlling the reconnection process and therefore highly influences the perturbation in the Earth's magnetosphere.
How to cite: Verbanac, G., Bandić, M., Ivanković, L., and Živković, S.: Characteristics of the Geoeffective Component of the Interplanetary Magnetic Field, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8168, https://doi.org/10.5194/egusphere-egu26-8168, 2026.
Solar wind–magnetosphere interaction is a major driver of global plasma convection in planetary magnetospheres. In Earth's magnetosphere, this convection is governed by magnetic reconnection on the dayside and nightside. Dayside reconnection alone can rapidly re‐establish convection within closed field lines, typically within 10–20 min following a southward turning of the interplanetary magnetic field (IMF). In this study, we show that solar wind speed strongly regulates the evolution and structure of this convection. Using global magnetohydrodynamic (MHD) simulations under the condition, we compare the magnetospheric response to southward IMF turnings under fast (800 km/s) and slow (400 km/s) solar wind streams. In the fast stream case, enhanced convection extends from the dayside magnetopause to 20 RE down the magnetotail within 15 min, compared to approximately 20 min in the slow stream case. The fast stream also drives deeper and more intense convection, accompanied by stronger Region 1 field‐aligned currents (FACs) and enhanced flow shear in the low‐latitude boundary layer. In both fast and slow wind cases, the induced convection exhibits discrete spatial and temporal channels. These results demonstrate that solar wind speed is a key parameter controlling the development of induced magnetosphere convection, with important implications for global solar wind– magnetosphere coupling.
How to cite: Zhu, M., Dai, L., Ren, Y., Wang, X., Wang, T., Wang, K., and Wang, C.: Response of Magnetospheric Convection to the Southward Turning of the IMF in Fast and Slow Solar Wind Streams, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8547, https://doi.org/10.5194/egusphere-egu26-8547, 2026.
We conducted a statistical study on the orientation of field-aligned currents (FACs) sheets in the high latitude fields of the Northern Hemisphere (NH) and Southern Hemisphere (SH) under different seasonal conditions, interplanetary magnetic field (IMF), and geomagnetic activity. We use the maximum correlation method to analyze nearly 9 years of measurements from Swarm A and C satellites. The orientation of the FAC sheets during each aurora oval crossing and the corresponding angle between the FAC sheets and the aurora boundary are derived. We find that under all conditions, the dawnside FAC sheets are clockwise at the aurora boundary, while the duskside are counterclockwise, which is similar to the flow pattern of auroral electrojet currents (AEJs) (westward on dawnside, eastward on duskside), indicating that AEJs may limit the spatial arrangement of FAC sheets. IMF By will affect the dawn-dusk asymmetry of FAC sheets arrangement, and enhanced geomagnetic activity will cause FAC sheets in both hemispheres to develop towards a more regular arrangement direction. In addition, the hemisphere and seasonal differences in FAC sheets arrangement may be related to changes in ionospheric conductivity. Our findings provide important information for the dynamic modulation of the ionospheric current system driven by external forces. In the future, the combination with SMILE satellite data will help to improve the M-I coupling model.
How to cite: Zhang, C., Malcolm, D., Yang, J., Xiong, C., Cao, J., and Tan, X.: A Statistical Study of Field-Aligned Current Sheet Orientation: Dependence on Season, Hemisphere, and Solar Wind Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9058, https://doi.org/10.5194/egusphere-egu26-9058, 2026.
The solar wind magnetosphere interaction has been studied since the first spacecraft in-situ observations in the late 60s. Since then, many missions have made observations of this interaction, first with single point measurements and later using multi-point observations. These observations however lack the full view of the magnetosphere and only statistical studies over long periods of time have been able to provide a global perspective. The SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission will give an instantaneous image of the dayside magnetosphere and its interaction with the impinging solar wind.
SMILE is a novel self-standing mission dedicated to observing the solar wind - magnetosphere coupling via simultaneous soft X-ray imaging of the magnetosheath, magnetopause and polar cusps, UV imaging of the northern hemisphere auroral oval and in situ solar wind ion and magnetic field measurements. Remote sensing of the magnetosheath and cusps with soft X-ray imaging is made possible thanks to solar wind charge exchange (SWCX) X-ray emissions known to occur in the vicinity of the Earth's magnetosphere. SMILE is a joint mission between ESA and the Chinese Academy of Sciences (CAS) due for launch in quarter 2 of 2026 from Kourou on a Vega C rocket. SMILE science goals as well as the latest scientific and technical developments, jointly undertaken by ESA, CAS and the international instrument teams, will be presented. SMILE will be complemented by ground-based observatories as well as by theory and simulation investigations. A special issue of Space Science Reviews presents the science, mission, spacecraft, instrument, ground segment, modelling activities and public engagement (https://link.springer.com/collections/cfeghhfceb).
How to cite: Escoubet, C.-P., Forsyth, C., and Wang, C. and the SMILE team: Imaging the solar wind – magnetosphere interaction with SMILE, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9748, https://doi.org/10.5194/egusphere-egu26-9748, 2026.
How to cite: Gurev, D., Kronberg, E. A., Shprits, Y. Y., Smirnov, A., Mihaljcic, B., and Fazakerley, A. N.: Global Empirical Modeling of Magnetospheric Electrons for MIT Research, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13403, https://doi.org/10.5194/egusphere-egu26-13403, 2026.
In this paper we present a numerical study on the soft X-ray detection of high-speed plasma jets that are moving within the terrestrial magnetosheath. For this purpose, we developed a simulation approach able to provide X-ray images from a virtual soft X-ray telescope launched inside the simulation domain. Our methodology is based on global MHD simulations of the magnetosphere coupled with a kinematic approach on the propagation of jets. The soft X-ray emission is calculated using a fluid-like quantification of the solar wind charge exchange process. We considered different parameters for the high-speed plasma jets and tested various setups for the virtual soft X-ray telescope. The numerical solutions show that, under certain circumstances, the soft X-ray signature of high-speed plasma jets is visible in the magnetosheath. We discuss here the implications of our results for the upcoming Solar wind-Magnetosphere-Ionosphere Link Explorer (SMILE) mission. SMILE is a joint mission of the European Space Agency and Chinese Academy of Science that shall be launched in spring 2026 to observe in soft X-rays the interaction between the solar wind plasma and the terrestrial magnetosphere. Also, we discuss the potential implications of our simulations for future soft X-ray telescopes.
How to cite: Voitcu, G., Echim, M., Teodorescu, M., and Munteanu, C.: X-ray detection of jets in the terrestrial magnetosheath: Implications for SMILE mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19584, https://doi.org/10.5194/egusphere-egu26-19584, 2026.
The spatial distribution of energetic O+ ions in the dayside outer and inner magnetosphere during the early recovery phase of the May 2024 superstorm is observed by MMS satellites over a 10-minute interval. During this short interval, the solar wind dynamic pressure sharply decreases from 40 nPa to 10 nPa, leading to the magnetopause expanding sunward. O+-rich plasma is found in the dayside magnetosheath with high O+ ion number density, Nmax_O+ ~ 4.8 cm-3, and the number density ratio of O+ to H+ is about 0.1. O+ ions in the magnetosheath have energies in the range 3-40 keV. O+ ions, escaping from the ring current, are perpendicularly accelerated by the intense electric field, Ex ~ 50 mV/m, at the dayside magnetopause with high reconnection outflow ~260 km/s into the magnetosheath. The escape of energetic O+ ions, with high number density and temperature, from the ring current into the magnetosheath results in the rapid decay of the ring current energy flux during the early recovery phase of this superstorm. This O+ ion escape can cause the SYMH index to recover by 16 nT. Our study provides evidence for a high-energy O+ ion flux in the magnetosheath, which drives the efficient decay of the ring current and the rapid early recovery phase observed during the May 2024 superstorm.
How to cite: Duan, S., Dai, L., He, Z., and Wang, C.: Contribution of energetic O+ ion escape into the magnetosheath to rapid recovery of the May 2024 superstorm observed by MMS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22864, https://doi.org/10.5194/egusphere-egu26-22864, 2026.
Ion-electron decoupling at ion scale lead to Hall effect, the indicative process of collisionless magnetic reconnection. Past observations have revealed the features of Hall current system in L direction, Hall magnetic field in M direction and Hall electric field in N direction. However until now, there is no observations on the ion-electron decoupling（Hall current）in N direction, where Hall effect originates. In this study, using MMS observation, we find ion-electron decoupling（Hall current）in N direction in the separatrix region at the magnetospheric side of a reconnection current sheet. A comprehensive analysis provides the insight to the process of ion-electron decoupling, regarding electron motion, composition of Hall electron, and charge distribution. From micro mechanism, the results deep our understanding of solar wind-magnetosphere coupling triggered by reconnection, and support the upcoming study based the observation from launched SMILE mission.
How to cite: Zhang, Y. C., Dai, L., and Wang, C.: Direct observation of ion-electron decoupling in magnetic reconnection , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22866, https://doi.org/10.5194/egusphere-egu26-22866, 2026.
Using ground-based magnetometer data and GNSS data from the Chinese Meridian Project, we investigate ULF wave within Pc4 frequency bands modulating total electron content (TEC) of ionosphere in the midlatitude region, during the period of 2024 Mother Day Geomagnetic Storms. The amplitude of PC4 wave can reach 56.5nT, which is the largest amplitude of PC4 in the midlatitude region. This geomagnetic field disturbance account for 0.025% of background geomagnetic field, while it can trigger a ten-times, i.e., 0.25% TEC variation. The amplitude of TEC variation can reach to 0.4 TECU, which is 3 times of the TEC variation in quiet day. This modulation process covers a wide space region with 40 longitude span of 40 degrees and latitude span of 20 degrees. These results provide us new knowledge about the coupling between the solar wind-magnetosphere-ionosphere in midlatitude regions, and have the potential significance on evaluating the effect of space weather of this coupling process.
How to cite: Cheng, M. T. and Zhang, Y. C.: The Characteristics of Ionosphere Modulation by Magnetosphere Ultra-low Frequency Waves During 2024 Mother Day Geomagnetic Storms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22868, https://doi.org/10.5194/egusphere-egu26-22868, 2026.
We report a Kelvin-Helmholtz vortex (KHV) event observed at the dusk-side low-latitude boundary layer by the Magnetospheric Multiscale (MMS) satellites, in conjunction with auroral beads detected in the high-latitude ionosphere by the Defense Meteorological Satellite Program (DMSP) on 27 September 2016. During this KHV event, MMS traversed the low-latitude boundary layer (LLBL), magnetically mapping to the DMSP auroral footprint. MMS revealed small-scale substructures embedded within the KHVs. These structures are associated with intense field-aligned currents (FACs) connecting the magnetospheric boundary layer to the ionosphere. These FACs are capable of driving aurora precipitations, forming discrete auroral beads. The ~1200 km KHV scale and ~50 km auroral electron precipitation scale are consistent with magnetosphere-ionosphere flux tube mapping. These observations provide evidence that small-scale auroral beads are ionospheric signatures of mesoscale KHVs, highlighting the role of boundary layer instabilities in regulating magnetosphere-ionosphere coupling.
How to cite: Hou, Y., Duan, S., Dai, L., and Wang, C.: Kelvin-Helmholtz Vortices in the Low-latitude Boundary Layer Associated with Auroral Beads: Conjunction Observations from MMS and DMSP, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22870, https://doi.org/10.5194/egusphere-egu26-22870, 2026.
Based on high-resolution measurements from NASA’s Magnetospheric Multiscale mission (MMS), we present the first direct observation of an ion diffusion region (IDR) with high number density O+ ions within the dayside magnetopause reconnection during the May 2024 superstorm. The O⁺ ion density reaches a high value of ~3.3 cm⁻³. It helps study heavy-ion dynamics in dayside magnetopause reconnection. In the vicinity of IDR, O⁺ ions exhibit distinct acceleration to 300 km/s along the normal direction caused by the enhanced Hall electric field (ENmax≈ 80 mV/m). The distorted ion velocity distributions reveal the complex energization processes in the ion diffusion region. Crucially, these O⁺ ion dynamics can reduce the reconnection rate by ~ 25.3%, providing the result that heavy-ion dominance alters magnetopause reconnection physics during the superstorm. This study advances our understanding of magnetopause reconnection by demonstrating that storm-enhanced O⁺ populations modify the structure of diffusion regions, particle energization, and the reconnection rate.
How to cite: Anxin, Z., Duan, S., Dai, L., Hou, Y., Ren, Y., Wang, C., Fuselier, S., Escoubet, P., and Burch, J.: Observations of the magnetopause reconnection ion diffusion region with high-density O+ ions during the May 2024 superstorm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22874, https://doi.org/10.5194/egusphere-egu26-22874, 2026.
Geomagnetic storms represent a major manifestation of the magnetospheric response to transient solar wind forcing, that carries structures such as shock waves, interplanetary coronal mass ejections, stream interaction regions, and so on. Previous studies have shown that the magnetospheric response cannot be described by purely deterministic dynamics, and also consists of strong sudden fluctuations developing across multiple scales. Such dynamics have been extensively modeled using stochastic differential equations, which provide a natural framework to describe the combined effects of large-scale driving and stochastic fluctuations in physical systems. For univariate models, e.g., based on a single geomagnetic index, the fluctuating character of the internal magnetospheric dynamics represents the response to the unresolved external driving, whose influence manifests as stochastic variability. This work extends univariate descriptions by developing a bivariate stochastic model that explicitly accounts for the coupling between magnetospheric dynamics and interplanetary magnetic field. We use the geomagnetic index SYM-H, which is a proxy of the large-scale ring current state, and the Bz component of the magnetic field as representative of the external driver. The potential of this model in the context of space weather is discussed.
How to cite: Taheri, R., Consolini, G., and Benella, S.: Bivariate stochastic modeling of the magnetospheric dynamics driven by solar wind forcing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7231, https://doi.org/10.5194/egusphere-egu26-7231, 2026.
Energetic particles injected from dayside reconnection serve as a source for ionospheric particle precipitation in the cusp region. The cusp comprises poleward-moving plasma structures, cusp plasma filaments due to discontinuous reconnection events which are considered footprints of flux transfer events (FTEs). These structures remain relatively unexplored on Earth, however an examination of MESSENGER data from Mercury's magnetosphere suggests that cusp filaments represent the magnetospheric extensions of FTEs originating at the magnetopause due to localized magnetic reconnection. This underscores the need for a comprehensive investigation of similar phenomena within Earth's magnetosphere. Reconnection often takes place at the dayside magnetopause, where the solar wind's magnetic field interacts with the Earth's magnetic field. This interaction leads to the merging and rearrangement of magnetic field lines, creating open magnetic field lines that connect the high-latitude magnetospheric cusp to the solar wind forming FTEs which are flux-rope-like structures filled with magnetosheath plasma. In this study, data obtained from the MMS spacecraft was examined which is strategically positioned to traverse the cusp region. The spacecraft's orbit facilitates multi-spacecraft in situ measurements within the cusp, providing crucial data for the analysis of phenomena such as cusp plasma filaments. Cusp filaments were analyzed using multi-spacecraft analysis techniques and high-resolution measurements were utilized to reconstruct and analyze the internal plasma structure of these cusp filaments. Characteristics and spatial distribution of cusp plasma filaments within Earth's cusp region were also investigated. The primary focus was to comprehend the role of these filaments in particle precipitation and their correlation with dayside magnetic reconnection events. Our preliminary results suggest that cusp plasma filaments are indeed low latitude, high altitude footprints of FTEs. Moreover, there appears to be a correlation between the presence of plasma filaments and dayside reconnection events.
How to cite: Agarwala, N., Poh, G., Sun, W., Chen, Y., Slavin, J. A., and Le, G.: Effects of Magnetic Reconnection Dynamics in Earth's Cusp: Investigating Plasma Filaments and Flux Transfer Events using MMS Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22408, https://doi.org/10.5194/egusphere-egu26-22408, 2026.
The plasmasphere is a torus of cold plasma ‘frozen’ into the Earth’s magnetic field, sourced from the ionosphere. Drainage channels, called plumes are formed during disturbed periods by the modified electric field. While plumes have been primarily observed near the equator, the electric field driving then acts along the entire geomagnetic field line, setting the plasma within a complete drift shell into motion. Ionospheric evidence of this process is found in the so-called Storm-Enhanced-Density plumes, which also exhibit density surplus compared to the background. These findings led to the establishment of the geospace plume concept. However, this same process creates other features in the ionosphere, like the midlatitude trough, a zone of depleted plasma density. The relationship between plasmaspheric plumes and the ionospheric trough has been neglected in previous studies. Our findings challenge the current understanding of the geospace plume concept and underscore the need for its refinement.
How to cite: Heilig, B. and Tomasik, M.: Ionospheric traces of plasmaspheric plumes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20038, https://doi.org/10.5194/egusphere-egu26-20038, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 4
EGU26-15149 | ECS | Posters virtual | VPS28
Magnetosphere response to a spatially non-uniform solar wind streamThu, 07 May, 14:00–14:03 (CEST) vPoster spot 4
Interpreting the response of the magnetosphere to solar wind driving is being historically limited by the sparse measurements of upstream conditions. Recent investigations, using multiple upstream monitors, revealed that properties of the solar wind are often non uniform on spatial scales comparable to the size of the Earth’s magnetosphere. This aspect remarks the limitation of the common assumption of the impact of a uniform solar wind front based on single probe observations. Here, we perform a critical investigation of a case study in which a particular solar wind mesoscale structure, in the form of a periodic density structure (PDS), shows coherence on a limited extent of the Earth’s upstream region. First, we examine the possible reasons behind discrepancies in the measurements among different solar wind monitors. Then, we discuss the response of the magnetosphere in terms of Ultra-Low-Frequency (ULF) waves based on properties of the solar wind driver including the periodicities of the PDSs, the extent of their spatial coherence, and the associated interplanetary magnetic field properties.
How to cite: Di Matteo, S., Recchiuti, D., and Villante, U.: Magnetosphere response to a spatially non-uniform solar wind stream, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15149, https://doi.org/10.5194/egusphere-egu26-15149, 2026.
