Orals: Tue, 5 May, 10:45–12:30 | Room L1
Magnetic reconnection is a fundamental energy conversion process in plasmas. While
changes in the topology of the magnetic field take place inside a small region, acceleration and heating of the plasma are distributed over larger scales. Acceleration and heating drive plasma transport and lead to explosive magnetic energy release likewise on large scales during phenomena such as substorms, solar flares, and possibly gamma ray bursts. With modern space technology, geospace is an ideal plasma laboratory for studying how collisionless magnetic reconnection operates in nature since plasmas and fields in action can be directly measured at high cadence. With the advanced in-situ measurement capability to resolve electron-scale physics, the four Magnetospheric Multiscale (MMS) spacecraft have significantly advanced the study of magnetic reconnection and relevant plasma processes. In this presentation we highlight unsolved problems of magnetic reconnection in collisionless plasma. Advanced in-situ plasma measurements and simulations have enabled scientists to gain a novel understanding of magnetic reconnection. Nevertheless, outstanding questions remain concerning the complex dynamics and structures in the diffusion region, cross-scale and regional couplings, the onset of magnetic reconnection, and the details of particle energization. We discuss future directions for magnetic reconnection research, including new observations, new simulations, and interdisciplinary approaches.
How to cite: Nakamura, R. and Burch, J. L. and the Outstanding Questions of Magnetic Reconnection Team: Outstanding Questions and Future Research on Magnetic Reconnection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4296, https://doi.org/10.5194/egusphere-egu26-4296, 2026.
To understand the physical processes of the steady solar wind-magnetosphere system, two aspects must be considered: (i) the dynamical processes, which govern the distribution of mass, momentum, and energy, and (ii) the magnetic field topology, which governs the three-dimensional reconnection between the solar wind and the magnetosphere. Because the magnetic topology is determined by the combined interplanetary magnetic field (IMF) and geomagnetic field, the solar wind and magnetosphere should be treated as a single magnetohydrodynamic (MHD) fluid system. In this unified system, the physical processes can be interpreted as the interaction between the plasma and the magnetic field. When the plasma is absent, a vacuum magnetic-field configuration emerges, representing the system's ground state. Therefore, the dynamics of the system can be described as a balance between two forces: a force returning the magnetic field to its ground state and a force exerted by the solar wind plasma that deforms the magnetic field lines. This framework is referred to as the mechanical principle. The vacuum magnetic field exhibits a characteristic topology with two null points and two separators, which provide the magnetic framework for separator reconnection. Global MHD simulations have confirmed that this topology is preserved under northward IMF conditions, a property we refer to as the topology conservation property. Both the mechanical principle and the topology conservation property together determine the magnetic field structure of a quasi-steady solar wind-magnetosphere system. Therefore, this study achieves a fundamental understanding of the interaction between magnetic topology and plasma dynamics in the solar wind-magnetosphere system in the northward IMF conditions. Within this framework, we discussed that both the topology conservation property and the mechanical principle play essential roles in the formation of the steady-state magnetic field structure of the magnetotail and the plasma sheet in the northward IMF condition.
How to cite: Fujita, S., Watanabe, M., Tanaka, T., and Cai, D. S.: Fundamental physical processes of the steady solar wind-magnetosphere system under northward IMF conditions in the framework of the magnetic topology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7351, https://doi.org/10.5194/egusphere-egu26-7351, 2026.
The joint mission between the European Space Agency and the Chinese Academy of Sciences, the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE), is due to launch in spring 2026. The Soft X-ray Imager (SXI) on board SMILE will measure X-rays emitted from the magnetosheath and cusps. These data will help trace variations in the positions of the magnetopause and cusps in response to changes in the solar wind. We present a fast, computationally inexpensive method for determining the magnetopause standoff distance using a set of simulated X-ray images. We demonstrate that the standoff distance can be obtained with an accuracy better than 0.5 RE using a 1-minute integration time when the magnetosphere is significantly compressed. We also discuss the differences between emissions produced by the magnetosheath and the cusps, as well as the role of spacecraft position in SXI data analysis.
How to cite: Samsonov, A., Forsyth, C., Sembay, S., and Carter, J. A.: How accurately can we find the magnetopause standoff distance using SMILE SXI?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10440, https://doi.org/10.5194/egusphere-egu26-10440, 2026.
In Earth’s polar regions, Field-Aligned Electrons (FAEs) have been studied for decades. However, their response to solar wind and IMF conditions still require further investigation. In this study, we used Cluster observation data to examine the influence of solar wind and IMF on polar region FAEs. The FAE event was selected based on an electron flux threshold exceeding 3×108 cm-2s-1 for analysis. Several notable findings were obtained. (1) FAE occurrence rates increase with solar wind dynamic pressure (Psw) increasing for both upward and downward FAEs. In the northern hemisphere, however, the occurrence rates appear to rise more sharply than in the southern hemisphere. (2) The distribution of FAE occurrence shows two peaks in relation to IMF By: a major peak around IMF By = -20 nT and a minor peak around IMF By = +20 nT. (3) FAEs occur most frequently when IMF Bz>0 and IMF By>0, which corresponds to an IMF clock angle between 12:00 and 03:00. (4) Since geomagnetic activity is driven by solar wind–magnetosphere interaction, we also examined FAE occurrence in relation to the geomagnetic activity Kp and AE indices. The results indicate that FAE occurrence depends primarily on increasing AE activity. We discuss potential mechanism underlying these results. Variation in FAE occurrence appears to be largely controlled by magnetospheric configuration and its response to solar wind conditions. Further analysis suggests that FAE are closely associated with FAC in polar space. It is significant to understand the physical process in the polar region.
How to cite: Shi, J., Cheng, Z., and Escoubet, P.: Solar Wind/IMF Influences on Field-Aligned Electrons in Earth’s Polar Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12038, https://doi.org/10.5194/egusphere-egu26-12038, 2026.
Data from SAMPEX, POLAR, and other spacecraft have previously shown that high energy electrons (E ≳ 1 MeV) vary in a remarkably coherent way throughout the entire outer radiation zone of the Earth (2.5 ≲ L ≲ 6.5). Such data have been used to perform analysis of the flux variations of relativistic electrons throughout the outer Van Allen zone. This talk reports similar analyses of Van Allen Probes data from the REPT sensor system from 2012 to 2019. Averages are performed for monthly intervals centered on the spring and fall equinoxes and on the winter and summer solstices. Modulation is deonstrated such that equinoctial fluxes of electrons are larger than the solstitial fluxes by large factors based upon a superposed epoch analysis. These semiannual modulations of relativistic electron fluxes are compared with concurrent solar wind data. Results are also examined in terms of prior models of geomagnetic activity acceleration processes.
How to cite: Baker, D. N. and Kanekal, S. G.: Equinox and solstice averages of magnetospheric relativistic electrons: Strong semiannual modulation of fluxes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8230, https://doi.org/10.5194/egusphere-egu26-8230, 2026.
We use the REPT (relativistic Electron Proton Telescope) data onboard the Van Allen Probes mission to examine the penetration of solar energeetic Helium into the magnetosphere. Specidfically we the pulse height analyzed data (PHA) in the REPT solid state detector stack for each individual particle measured. we identify SEP-He is by using active periods with identified SEP events. We will specifically focus on the large SEP events that occurede during the September of 2017. Using PHA data we derive the incident spectrum nd its evolution during the event. From a space weather perspective It is important note that He ions deposit energy through rapid ionization resulting in single event upsets (SEU) whereas protons do that via nuclear interactions.
How to cite: Kanekal, S., Gautier, F., Baker, D., Greeley, A., and Schiller, Q.: Solar energetic He transport into the Van Allen radiation belts during intense SEP event of September 2017., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11480, https://doi.org/10.5194/egusphere-egu26-11480, 2026.
Escape to space of thermal ions which originate in the Earth's ionosphere is still poorly understood. The dominant loss process from the modern Earth is a non-thermal escape mechanism called the polar wind, which is currently dominated by ionized oxygen. The oxygen ions are accelerated by various physical processes, such as electric fields and wave-particle interactions, and escape to space from the polar regions. I present the new test-particle code KISEL (KInetic Simulator of Escaping Light ions), which can reproduce the main features of the cold polar outflow from the Earth and can be applied to other planets. We can reproduce the typical observed range of O+ loss rate from the Earth of 1024-1026 s-1 depending on solar activity. We model the escape during the Gannon storm and obtain a range of escape rates typical for high kp-index conditions. We show that the ambipolar electric field plays a decisive role in uplifting the cold ions and allowing them to escape, and confirm previous findings that only a minor fraction of cold ions produced in the whole ionosphere escape to space (approximately 2\% of oxygen ions for typical quiet conditions). To study the parallels between the present-day Earth and the early Earth, we also simulate the ion escape from the Earth at the age of approximately 300 million years. We show that, first of all, the dominant escape ion is C+ and not O+ like today, and second, that a much higher fraction of initially cold ions (approximately 20%) can escape to space.
How to cite: Kislyakova, K., Sasunov, J., Raorane, A., Van Looveren, G., Macdonald, E., Metodieva, Y., Müller, L., Johnstone, C., Boro Saikia, S., Scherf, M., and Lammer, H.: Atmospheric escape of cold ions from the current and early Earth under different magnetospheric conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11199, https://doi.org/10.5194/egusphere-egu26-11199, 2026.
The magnetic field in the magnetosheath is approximately current-free and can therefore be described by a scalar potential satisfying the Laplace equation. A key difficulty in solving the Laplace equation numerically is the closure of the computational domain, as the downstream magnetosheath field is generally unknown. Here, we address this challenge by prescribing magnetic field data on the boundaries, obtained from an analytical model and a global plasma simulation. The Laplace equation is solved using a finite-difference Jacobi scheme with Neumann boundary conditions and a consistent treatment of curved boundaries. The method is demonstrated for Mercury’s magnetosheath using hybrid plasma simulation data under average solar wind conditions, showing that the large-scale field can be reconstructed self-consistently from the boundary constraints.
How to cite: Holzkamp, H. and Narita, Y.: Numerical solution of the Laplace equation for magnetosheath modeling using data-driven boundary conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12791, https://doi.org/10.5194/egusphere-egu26-12791, 2026.
ESCAPADE is a twin-spacecraft low-cost Mars mission that will revolutionize our understanding of how space weather conditions drive magnetic structure and flows of energy and momentum throughout Mars’ unique hybrid magnetosphere, and how this interaction drives both ion escape and sputtering escape. ESCAPADE will measure magnetic field strength and topology, suprathermal ion distributions and electron flows, and thermal electron and ion densities, as well as possibly image visible aurora. Our 2-part scientific campaign of temporally and spatially-separated multipoint measurements in different regions of Mars’ diverse plasma environment, will allow us to untangle spatial from temporal variability, characterize short-term variability, and unravel the cause-and-effect of solar wind control of magnetospheric structure and ion and sputtering escape for the first time.
ESCAPADE launched on November 13, 2025. Though it is a Mars mission, ESCAPADE’s journey begins with a 12 month “loiter” phase within ~2.5 million km of earth, primarily on the anti-sunward side, looping around the L2 Lagrange point and passing twice through the Earth’s magnetotail, at ~320 and again at ~80 earth radii. Instruments are due to be turned on in late February 2026, just prior to this first tail passage. ESCAPADE will provide the first two-point measurements of heliospheric conditions in these regions of space, addressing questions of solar wind and space weather structure on ~105 km scales and investigating distant magnetotail features, including spatial extent, dependence on solar wind conditions, and the existence of reconnection in the distant magnetotail. In November 2026, ESCAPADE will execute Oberth maneuvers at a ~500 km perigee to start their interplanetary journey, arriving at Mars in September 2027 and beginning their science mission in spring 2028. This presentation will focus on first results from the plasma instruments in the near-Earth heliospheric environment.
How to cite: Lillis, R., Xu, S., Curry, S., Hara, T., Livi, R., Whittlesey, P., Espley, J., Gruesbeck, J., Barjatya, A., Hanley, G., and Yusuke, E. and the The ESCAPADE team: Not just a Mars mission: First measurements from ESCAPADE in the Near-Earth Heliosphere and Distant Magnetotail. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5832, https://doi.org/10.5194/egusphere-egu26-5832, 2026.
The solar wind velocity monitor at the Sun-Earth L1 point (SOHO, ACE, DSCOVR) has been used to estimate the arrival time of interplanetary (IP) shocks associated with coronal mass ejections (CMEs) and corotating interaction regions (CIRs). In this estimate, the radial propagation speed of the IP shock is assumed to be the same as the measured solar wind (proton) speed. However, near the Sun, the CME front identified by SOHO LASCO imager sometimes propagates at velocity >1000 km/s, being faster than solar wind velocity measured at L1 (e.g., Tokumaru et al., 2006). Even after considering the deceleration of CME propagation with distance, these two speeds at 1 AU are not guaranteed to be the same.
We compared these speeds: between the solar wind and the radial propagation of the IP shock front. We used SOHO and ACE spacecraft data for the velocity and IP shock timing at L1, and geomagnetic data (geomagnetic sudden commencement: SC) for the IP shock timing at the Earth. We examined about 400 IP shock events that are consistent between SOHO and ACE during more than two solar cycles. We found the following tendency.
(1) The estimated arrival time driven from geomagnetic SC is often quite different from expected arrival time of the IP shock from the L1 velocity measurement.
(2) The estimated propagation velocity of the IP shock was from 80% to > 200% of the solar wind velocity.
(3) For a majority of the cases, the SC-estimated propagation velocity is slightly faster than the measured solar wind proton velocity, and is rather close to the velocity of the solar wind alpha particle.
The upcoming SMILE mission will give extra dataset for the arrival of the IP shock for further study.
How to cite: Yokoyama, Y., Yamauchi, M., Kotani, T., and Matzka, J.: Large difference in radial speed between the interplanetary (IP) shock propagation and the solar wind near the Earth., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11891, https://doi.org/10.5194/egusphere-egu26-11891, 2026.
Long-lasting quasi-radial interplanetary magnetic field (IMF) events represent a distinct class of solar wind conditions characterized by an unusual magnetic field orientation. Unlike typical solar wind intervals, these events deviate significantly from the nominal Parker spiral configuration, leading to altered large-scale spatial correlations of the IMF. In this study, we investigate the spatial correlation characteristics of long-lasting quasi-radial IMF events and compare them with those observed during normal Parker spiral conditions. Quasi-radial IMF events are identified using the criterion Bx / B >0.9 sustained for more than 4 hours, following a definition similar to that adopted in previous studies. Applying this criterion to Wind magnetic field observations from 2001 to 2024, we identify a total of 753 long-lasting quasi-radial IMF events. We calculate correlation coefficients between Wind and ACE magnetic field measurements without applying a time shift, thereby focusing on the intrinsic spatial correlation rather than propagation effects. The correlation analysis is performed for multiple magnetic field parameters, with particular emphasis on the magnetic field magnitude. Our results indicate that, during quasi-radial IMF conditions, the correlation coefficient of the magnetic field magnitude exceeds that of typical Parker spiral intervals when the spacecraft separation distance is greater than approximately 30 Re. However, within the intermediate separation range of roughly 30–150 Re, the correlation values are generally lower than those observed during Parker spiral conditions, suggesting a scale-dependent modification of IMF coherence under quasi-radial configurations. These findings imply that long-lasting quasi-radial IMF events exhibit distinct spatial correlation behaviors compared to nominal solar wind conditions, potentially reflecting differences in solar wind structure, turbulence properties, or magnetic field topology.
How to cite: Pi, G., Nemecek, Z., and Safrankova, J.: Correlation coefficient of long-lasting quasi-radial IMF events , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5423, https://doi.org/10.5194/egusphere-egu26-5423, 2026.
Plasma structures with the enhanced dynamic pressure, density, and/or bulk speed, commonly referred to as magnetosheath (MSH) jets, can be detected downstream of both quasi-perpendicular and quasi-parallel bow shocks. Although their presence in the MSH is well established, their true three-dimensional morphology, internal structure, and characteristic scales remain under active debate. Recent simulation results, suggesting filamentary interconnected jet structures, contrast with the simplified “pancake” or cylindrical geometries often inferred from single-spacecraft observations, highlighting the need of multi-point studies.
We present case studies of complex structure of MSH jets using coordinated measurements of THEMIS, MMS, and other missions. We focus on their spatial structure and temporal evolution as they propagate through the MSH, with attention to multi-spacecraft signatures in plasma and magnetic field parameters. Rather than drawing general conclusions, this work aims to illustrate the capabilities and limitations of multi-spacecraft observations for determination of jet morphology and evolution. We try to place individual events into the broader context of ongoing discussions. Particular attention is given to the interaction of the MSH jet with the magnetopause and its role in (localized) boundary dynamics.
How to cite: Grygorov, K., Goncharov, O., Safrankova, J., and Nemecek, Z.: Magnetosheath jets: morphology and evolution from multi-spacecraft observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8064, https://doi.org/10.5194/egusphere-egu26-8064, 2026.
Plasma structures with enhanced dynamic pressure, density or speed are often observed in Earth’s magnetosheath. These structures, known as jets and fast plasmoids, can be registered in the magnetosheath, downstream of both the quasi-perpendicular and quasi-parallel bow shocks Using measurements by the Magnetospheric Multiscale (MMS) spacecraft, Goncharov et al., (2020) showed similarities in the plasma properties of the jets and fast plasmoids. On the other hand, they pointed out that the different magnetic fields inside the structures suggest that the formation mechanisms are not the same. Previous studies established that foreshock structures can be a source of the jets (Raptis et al., 2022). Xirogiannopoulou et al. (2024) found that the subsolar foreshock contains several types of structures with enhanced density or/and magnetic field magnitude, like plasmoids, SLAMS and mixed structures. Following these results, we use multi-spacecraft data collected by THEMIS, Cluster, Magnetospheric Multiscale Spacecraft (MMS) and OMNI missions, and present analytical multi-spacecraft statistical and case studies on the connection between the activity around the bow shock. Based on our comparative analysis, we discuss features of jet-like structures, and their relation to the different phenomena in the foreshock.
How to cite: Goncharov, O., Xirogiannopoulou, N., Balot, P., Grygorov, K., Safrankova, J., Nemecek, Z., and Hajos, M.: Connection of the magnetosheath jet-like structures with foreshock activities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4405, https://doi.org/10.5194/egusphere-egu26-4405, 2026.
Plasma waves play a central role in the solar wind–magnetosphere interaction, especially in the foreshock and magnetosheath, where reflected particles, shock processes, and turbulence shape their properties. While these regions have been widely studied, the way foreshock waves evolve as they encounter the bow shock and how their downstream signatures relate to the upstream conditions remain poorly understood. Using multi-spacecraft observations from the MMS and/or THEMIS missions, we examine wave activity in the foreshock and characterize their key properties and put our findings in context with previous statistical results. We also present a statistical analysis of wave activity in the magnetosheath and compare it with the simultaneous measurements in both regions to explore how wave signatures change across the bow shock. This approach provides a more complete picture of how plasma waves vary across regions and offers new insight into their evolution in the near-Earth environment.
How to cite: Balot, P., Goncharov, O., Safrankova, J., Nemecek, Z., Xirogiannopoulou, N., and Grygorov, K.: Statistical study of wave activity in the foreshock and magnetosheath regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5486, https://doi.org/10.5194/egusphere-egu26-5486, 2026.
The Bernoulli principle, a fundamental concept in fluid dynamics, occupies an important position in the development of the discipline and finds wide application in both theory and engineering practice. In space plasmas, the Bernoulli equation can be derived from the continuity equation and the energy conservation equation. This presentation analyzes and presents the general form of the Bernoulli equation for multicomponent, non-equilibrium, and anisotropic space plasmas. Based on in-situ measurements from spacecraft such as ACE and MMS, this study examines the quantitative relationship between the plasma upstream (solar wind) and downstream (magnetosheath) of the Earth's bow shock. It confirms the applicability of Bernoulli’s theorem across the bow shock under both high-speed and low-speed solar wind conditions, demonstrating the existence of a conserved quantity—the characteristic energy of particles—along plasma streamlines. This indicates that Bernoulli’s theorem serves as an important theoretical tool for analyzing energy conversion processes across the bow shock and reveals a universal invariant—the particle characteristic energy—present in the upstream solar wind and throughout the downstream magnetosheath region. Applying Bernoulli’s theorem to the theoretical analysis of the relationship between solar coronal temperature and planetary magnetosheath temperature yields a quantitative relation that is consistent with statistical analyses of observational data from spacecraft such as MESSENGER, MMS, Voyager 2, and Cassini regarding thermodynamic parameters like the magnetosheath temperatures of planets (Mercury, Earth, Jupiter, and Saturn). These results hold significant value for studying the energy transfer mechanisms from the solar wind to magnetospheres and for understanding space weather in planetary magnetospheres
How to cite: Shen, C.: Bernoulli's Theorem in Space Plasmas and Its Applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17159, https://doi.org/10.5194/egusphere-egu26-17159, 2026.
The May 2024 geomagnetic superstorm was one of the most extreme space weather events of the past two decades. Starting from the Sun, a group of sunspots had grown significantly, producing a substantial solar flare and launching six coronal mass ejections (CMEs) and reaching the Earth, they significantly affected the Earth's magnetosphere. The Shue et al. (1998) model predicts the magnetopause position at a minimum distance of ~4 Re during the main phase of a storm, while the MHD (SWMF) model predicts a minimum at ~3.3 Re. To validate these models, we manually identified the magnetopause crossings observed by THEMIS, GOES, and MMS during the storm period. The crossings are identified by examining the multispacecraft data, and the impact of extreme conditions on the magnetopause location is determined. The observation and the Shue et al. (1998) model suggest that the magnetopause is compressed from 10 Re to 4 Re in a period of no more than 20 minutes. The manual identification from the multi-spacecraft data assumes that the magnetopause location is approximately 5 Re, and this result is consistent with predictions using various models. Moreover, the normal of each magnetopause crossing and its difference between the predicted normal from the Shue et al. (1998) model were calculated. The results can provide key insights into the dynamic magnetopause under extreme conditions.
How to cite: Ghosh, M., Wang, D., Haas, B., Lyu, X., Pi, G., Nemecek, Z., and Safrankova, J.: Validation of magnetopause positions predicted by models against multi-mission magnetopause crossings for the May 2024 superstorm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5547, https://doi.org/10.5194/egusphere-egu26-5547, 2026.
The subsolar standoff distance r0 of Earth's magnetopause is a key parameter in understanding the interaction between the solar wind and the magnetosphere. Despite decades of modeling efforts, significant uncertainties persist between model predictions and satellite observation of the magnetopause location. This study introduces a new data-driven parameterization of r0, based on a dataset containing over 220,000 dayside magnetopause crossings obtained by the THEMIS (2007-2022) and Cluster (2001-2020) missions. Four established magnetopause models are benchmarked against this dataset by computing the difference between predicted and observed r0, yielding root-mean-square errors (RMSE) of > 1 RE globally and > 0.8 RE in the subsolar region. Since different models use a variety of input parameters, it remains uncertain which parameters are most suitable to model the subsolar standoff distance of Earth's magnetopause to date. To address this question, a machine learning approach is used: an XGBoost regression model is trained and interpreted using SHapley Additive exPlanation (SHAP) values. The solar wind dynamic pressure is found to be the dominant contributor, followed by geomagnetic indices (AE, SYMH), interplanetary magnetic field (IMF) magnitude, dipole tilt angle, and IMF cone angle. The IMF Bz component contributes only marginally when geomagnetic indices are included. A support vector regression (SVR) model using the mentioned parameters achieves a RMSE of 0.68 RE, improving on the best analytic model by approximately 17%. To allow for straightforward modeling of the subsolar standoff distance, a second-order polynomial expression with 14 terms is derived, providing a compact, interpretable, and accurate representation of r0. We note that the SVR model and the polynomial representation is not able to predict r0 for extreme input conditions, e.g., during periods of very high solar wind dynamic pressure that is caused by, e.g., the passage of interplanetary coronal mass ejections. Accordingly, the parameter ranges that define the validity domain of the models are specified. We plan to broaden the range of possible input parameters in future iterations to account for, e.g., storm conditions as well. The presented results offer improved predictive accuracy of the subsolar standoff distance and highlight the potential of so far unconsidered parameters and rarely used techniques in modeling Earth's magnetopause.
How to cite: Klingenstein, L., Grimmich, N., Shprits, Y. Y., Grison, B., Lyu, X., Pöppelwerth, A., Wang, D., and Plaschke, F.: Parameterization of the Subsolar Standoff Distance of Earth’s Magnetopause based on Results from Machine Learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7269, https://doi.org/10.5194/egusphere-egu26-7269, 2026.
The Earth’s magnetopause is the boundary separating the terrestrial and the interplanetary magnetic field. Variations in solar wind pressure, as well as structures originating in the solar wind and foreshock regions, induce continuous motion of this boundary. In addition, strong velocity shear between magnetosheath and magnetospheric plasmas can trigger the Kelvin–Helmholtz instability. These processes can generate waves on the magnetopause that play a key role in governing mass transport and energy transfer between the solar wind and the magnetosphere.
Accurate estimation of the magnetopause wave vector is important for understanding interactions at the boundary. In this study, we compare different techniques for wave vector estimation. (1) Single-spacecraft methods require the determination of the boundary normal direction using approaches such as minimum variance analysis of the magnetic field (MVAB) or minimization of the Faraday residue (MFR), combined with estimates of the magnetopause phase velocity derived from ion measurements. (2) Cross-correlation analysis of magnetic field, density, and temperature measurements between different spacecraft allows estimation of wave vectors. In this context, modelling is used to explore potential systematic errors, for example arising from asymmetric waves, and to assess uncertainties in time-lag determination. (3) The wave telescope represents an alternative multi-spacecraft method to determine the wave vector.
Using observations from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, we apply these methods to several magnetopause wave events. We present preliminary results of this comparison, providing insight into the respective limitations and uncertainties.
How to cite: Pöppelwerth, A., Grimmich, N., Schulz, L., Klingenstein, L., and Plaschke, F.: Magnetopause surface waves: A comparison of wave vector determination techniques using THEMIS observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12517, https://doi.org/10.5194/egusphere-egu26-12517, 2026.
Sub-Alfvénic flows have been observed within magnetic clouds of interplanetary Coronal Mass Ejections (ICMEs), where enhanced magnetic field strength coincides with low plasma density. These conditions can significantly change the planetary space environment by enabling direct interaction between sub-Alfvénic solar wind and a planet’s magnetosphere. To investigate this regime, we perform a 3D global simulation using the hybrid code MENURA, modeling a plasma flow that transitions from super-Alfvénic to sub-Alfvénic as it encounters the magnetosphere. The upstream Alfvén speed is varied using a smoothed, step-like analytical function under pressure balance. The interplanetary magnetic field is oriented perpendicular to the Sun–planet direction, representative of local magnetic cloud conditions within ICMEs at 1AU. Our results reveal significant magnetospheric changes under sub-Alfvénic solar wind conditions: The bow shock rapidly weakens and dissipates while expanding to distances well beyond its original subsolar position, with pronounced expansion along the flanks. These findings provide new insight into magnetospheric dynamics under varying solar wind regimes and improve our understanding of planetary plasma environments. Furthermore, they offer valuable context for interpreting past observations from the MESSENGER mission and ongoing measurements from ESA’s BepiColombo mission.
How to cite: Preisser, L., Pucci, F., Ballerini, G., Henri, P., Sporykhin, F., and Wedlund, C. S.: Sub-Alfvénic solar wind interaction with a magnetosphere: 3D hybrid simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22070, https://doi.org/10.5194/egusphere-egu26-22070, 2026.
Coherent structures and random plasma variability at intermediate scales—between the large heliospheric structures such as interplanetary coronal mass ejections (ICMEs) and kinetic scales—have attracted growing attention within the solar wind and ICME community. This mesoscale variability in the solar wind has been shown to introduce uncertainty in the prescribed driving conditions of the magnetosphere, as in situ spacecraft upstream of the Earth’s magnetosphere do not always represent the actual solar wind forcing. Here, we demonstrate the global magnetospheric impacts of ICME mesoscale magnetic field variations. Using the Geospace configuration of the Space Weather Modelling Framework, we simulate the magnetospheric environment and, for the first time, capture a non-linear magnetospheric response that results from differences in the time-history of the driving conditions. Our results highlight the importance of understanding the longitudinal mesoscale variations in the solar wind to accurately interpret magnetospheric dynamics resulting from solar wind energy input into the system.
How to cite: Ala-Lahti, M., Pulkkinen, T., Brenner, A., Keebler, T., and Kilpua, E.: The global magnetospheric impacts of ICME mesoscale magnetic field variations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10518, https://doi.org/10.5194/egusphere-egu26-10518, 2026.
