New results focusing on the comparison of the latitudinal, seasonal and hemispherical effects of magnetic storms and substorms on the ionosphere are particularly welcome. Regarding atmospheric forcing, contributions focusing on atmospheric waves, wave-wave interactions, wave-mean flow interactions, atmospheric electricity, and electrodynamic coupling processes are sought. Contributions focusing on ionospheric effects from other sources, such as the solar terminator, solar eclipses, seismic activity or human-made explosions, are also welcome.
Machine learning approaches have shown remarkable results for the thermosphere, ionosphere, plasmasphere, and magnetosphere. This session also welcomes innovative approaches that include data assimilation, machine learning, empirical or numerical modeling to disclose interconnections and feedback within these complex systems.
Orals: Tue, 5 May, 08:30–12:25 | Room 0.94/95
In this study, we investigated the relationship between large-scale field-aligned currents (LSFACs) and simultaneous auroral particle precipitation using observations from the Defense Meteorological Satellites Program (DMSP). The dataset spans five years, from 1 January 2010 to 31 December 2014. Unlike previous studies that relied on the total flux, we analyzed auroral particle precipitation data measured separately by the 19 channels of the SSJ5 sensor to further investigate their relationship with typical Region 1 (R1) and Region 2 (R2) of large-scale FACs (LSFACs). Our results show that on the dusk-side, the central location of electron precipitation for the 19 channels cover the R1 FACs (upward). Specifically, the precipitation central location for 330 eV–440 eV electrons coincide with the R1 current central location. On the dawn-side, however, electron precipitation covers both R1 and R2 currents. We attribute this discrepancy to the different type of electron precipitation on the dusk- and dawn-side. Dusk-side electron precipitation is dominated by discrete aurora produced by parallel electric field acceleration, which is typically considered to be directly associated with FACs. And dawn-side electron precipitation is dominated by diffuse aurora, which we suggest does not directly generate LSFACs. The central locations of ion precipitation are roughly consistent on both the dawn and dusk sides, concentrating within the R1 FACs. Since R1 currents are upward on the dusk-side and downward on the dawn-side, this finding further demonstrates that ion precipitation is not directly related to LSFACs.
How to cite: Wang, S. and Xiong, C.: The Relationship between Large-Scale Field-Aligned Currents and Auroral Particle Precipitation at Different Energy Levels Based on DMSP Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2360, https://doi.org/10.5194/egusphere-egu26-2360, 2026.
Ion–neutral coupling in the lower thermosphere–ionosphere (LTI, ~100–200 km) is greatest in the form of Joule heating and impacts atmospheric models and satellite drag. However, the LTI remains significantly underexplored observationally, with only ~60 hours of in situ measurements below 200 km, particularly within the dayside polar cusp. The Cusp Region EXperiment-2 (CREX-2) sounding rocket mission provides a unique opportunity to study the LTI within the cusp. The CREX-2 payload carried various plasma instruments including four Mini Plasma Imagers (MPIs), developed at the University of Calgary, designed to measure cold plasma ion drift velocity and temperatures at high temporal and spatial resolution. In this presentation we describe efforts to estimate the bulk ion drift velocity from the MPI data, along with the measurement uncertainty, to explore the momentum coupling of the ionosphere with the thermosphere below altitudes of 200 km in the dayside cusp.
How to cite: Rupprecht, C. and Burchill, J.: Characterization of in situ ion drifts from the CREX-2 mission: implications for ionosphere-thermosphere coupling in the polar cusp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22045, https://doi.org/10.5194/egusphere-egu26-22045, 2026.
During the recovery phase of the major geomagnetic superstorm of 10-11 May 2024, for the first time, unusual vortex-like structures were observed in the thermospheric composition O/N2 ratio and thermospheric temperature by the Global-scale observations of the Limb and Disk (GOLD) instrument (Evans et al., 2024). The features occurred over the American and Atlantic regions, and were also partly seen in the vertical total electron (VTEC) content maps. After that first-time discovery, Correira et al. (2025) further reported the occurrence of similar vortices but of smaller magnitude and smaller spatial scale during the October 2024 superstorm and during the April 2023 storm. Correira et al. (2025) also mentioned no evidence of the occurrence of the vortices in VTEC during these storms.
In this work, we use data of the GOLD mission together with maps of GNSS-derived VTEC to study the correlation between the themospheric composition and the VTEC (Astafyeva et al., 2025). For the first time, we show that the lifetime and the evolution of the vortices in these two parameters differ: while the composition alters very slowly and the vortices slowly shift westward with their structure unchanged, the VTEC vortices can change very rapidly and their zonal drift is less evident. The link between the two parameters has been known for decades, however, the exact coupling remains poorly understood. The World’s most advanced simulation tools managed to reproduce the occurrence of an O/N2 vortex in the Southern Hemisphere, but not in the Northern Hemisphere (Wang et al., 2024). That same model or no other model was capable of reproducing such vortices in the VTEC during the May 2024 superstorm.
We also show that VTEC vortices can occur during other intense storms, which means that the ionospheric VTEC can serve, to some extent, as a proxy of storm-time changes in the thermospheric composition.
References:
Astafyeva, E., B. Maletckii, I.D. Ouar, M. Förster, D.R. Themens, J.D. Huba, M. Hairston, W.R. Coley, and M.-C. H. Fok. (2025) An extraordinary dayside negative ionospheric storm and total electron content (TEC) vortices observed on 11 May 2024. J. Geophys. Res. - Space Physics, V.130, N12, doi: 10.1029/2025JA034571.
Correira, J., J. S. Evans, J.D. Lumpe, R.W. Eastes, et al (2025) Upper Atmospheric Vortices Following Strong Geomagnetic Storms, Geophys. Res. Lett., V.52, N11, e2024GL113726, doi: 10.1029/2024GL113726
Evans, S., J. Correira, J.D. Lumpe et al. (2024) GOLD Observations of the Thermospheric Response to the 10–12 May 2024 Gannon Superstorm, Geophys. Res. Lett., V.51, 16, e2024GL110506, doi:10.1029/2024GL110506.
Wang, W., K.H. Pham, H. Wu, J.S. Evans, R.W. Eastes, D. Lin, V.G. Merkin (2024) MAGE (Multiscale Atmosphere-Geospace Environment) model simulations of the dynamic processes driving the thermospheric responses to the May 10, 2024 geomagnetic superstorm, AGU Annual Meeting, December 2024, Washington DC, USA
How to cite: Astafyeva, E., Maletckii, B., Ouar, I. D., Foerster, M., Themens, D. R., Huba, J. D., Hairston, M. R., Coley, W. R., and Fok, M.-H.: Observation of thermospheric and ionospheric vortices during geomagnetic storms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17528, https://doi.org/10.5194/egusphere-egu26-17528, 2026.
The Super Dual Auroral Radar Network (SuperDARN) radars operated by the University of Saskatchewan can now capture ionospheric plasma velocities at a very high temporal resolution (on the order of seconds), without compromising their several million square kilometres fields of view. When data from the five USask SuperDARN Canada radars are combined, a 2D ionospheric flow field can be derived that spans much of northern Canada and the polar cap. This new data product, updating nominally at a 3.7s temporal resolution, is called the Fast Borealis Ionosphere (FBI).
In this study, we use FBI data to study ionospheric flow “wigglyness”; the rapid (second-scale) variability of the ionospheric convection across a large region of the ionosphere. The scale sizes considered capture meso- and global-scale ionospheric processes, but at a temporal resolution that is usually only visible with spacecraft at small scales. We show that there is a significant amount of temporal variability even at scale sizes typically considered large, which alludes to the ubiquitous influence of Alfvén waves in the magnetosphere-ionosphere system.
How to cite: Billett, D., Mann, I., Rohel, R., and Hussey, G.: The wigglyness of the large-scale ionospheric convection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2850, https://doi.org/10.5194/egusphere-egu26-2850, 2026.
Ionospheric space weather (ISW) is formed when LEAIM system is impacted by powerful sources located above the ionosphere (from solar wind and magnetosphere during strong magnetic storms), within atmosphere-ionosphere (lightnings; instabilities in active nonlinear atmosphere-ionosphere), and below the ionosphere (in the lower atmosphere or within Earth, including hurricanes, earthquakes, and volcanoes). One of the key issues in understanding mechanisms of ISW formation is the study, modeling, and comparison with experiment of processes of interactions and propagation of wave disturbances in "vertical" and "horizontal" (latitude-longitude) directions in open dynamic active/dissipative LEAIM system, including the ionosphere. Synergistic approach required for such studies requires multiparameter ground-based and satellite methods for diagnosing ionospheric plasma structures (IPS), including Traveling Ionospheric Disturbances (TIDs). Radio diagnostics, including the use of GNSS data, LOFAR (Low-FRequency Radio Telescope Array), Ionosondes, VLF (Very Low Frequency/kHz) Radio Waves in the Earth-Ionospheric Waveguide, etc., constitutes an important part of radio diagnostic methods. In particular, methods and models for excitation of electromagnetic waves (EMW) and acoustic-gravity waves (AGW) by current and hydrodynamic/thermal sources are being developed and will be presented, including lightning sources EMWs in lower atmosphere and mesosphere associated with volcanoes; excitation of AGW and EMW by ground and lithospheric current sources associated with seismic processes; excitation by ionospheric current-thermal sources of AGW/IPS/TIDs (Travelling Ionospheric Disturbances), penetrating from upper to middle and low latitudes; these sources are located at high latitudes/auroral oval or middle latitudes, and they are associated with the penetration of magnetospheric currents into ionosphere during magnetic storms; solar terminator as a source of AGW/TIDs; developing Perkins instability in the middle-latitude ionosphere in the presence of AGWs as a seeding factor and radio wave scattering on the excited nonlinear IPS; models of scattering of high-frequency EMW/LOFAR (MHz) radio waves on IPS. The following breakthrough experimental-theoretical results in the field of atmospheric electricity theory will be presented. (1) Hunga Tonga volcano eradication (HTVE) (January 2022) caused unprecedented lightning currents in lower atmosphere of order 5*10-7 A/m2, exceeding fine-weather current by 5 orders of magnitude; unprecedented influence of radon on conductivity, electric and magnetic fields in the lower atmosphere in region of Popocatepetl volcano was discovered; electric field can exceed the fine-weather field by 5 orders of magnitude, with coronal discharge between charged cloud and volcano cone. Therefore seismogenic electromagnetic fields of ULF and ELF (Ultra- and Extremally Low frequencies, respectively) and VLF ranges penetrate into ionosphere and are capable to form ISW; (2) new model of planetary-scale MHD/AGW vortex structures gives spatial periods and velocities which are in agreement with ionospheric satellite observations; (3) combined complex-geometrical optics-beam method for radio weave scattering on the IPS/TIDs is developed; birefringence and dependence of radio wave frequency on the TID velocity is included; astrophysical sources are used as “projectors” irradiating the IPS under investigation, while LOFAR is used as a detector of the scattering waves; (4) new model of AGW/TIDs excitation by solar terminator provides characteristics parameters (periods, velocities) and tiny peculiarities of structures corresponding to GNSS and LOFAR observations.
How to cite: Rapoport, Y., Błaszkiewicz, L., Krankowski, A., Kownacki, M., Fron, A., Grimalsky, V., Escobedo-Alatorre, J., Tecpoyotl-Torres, M., Shelyag, S., Yutsis, V., Liashchuk, O., Przepiórka-Skup, D., and Cherniak, I.: Electromagnetic and acoustic-gravity wave coupling in Lithosphere (Earth)-Atmosphere-Ionosphere-Magnetosphere (LEAIM) system in «vertical» and «horizontal» directions and radio diagnostics , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21496, https://doi.org/10.5194/egusphere-egu26-21496, 2026.
We present observations and analysis of co-seismic infrasound in the ionosphere recorded by continuous Doppler sounding over Czechia and associated with the Kamchatka M8.8 earthquake on July 29 2025. The co-seismic infrasound was observed at a height of almost 340 km, which is much higher (by more than 100 km higher) than in previous Doppler sounding observations of co-seismic infrasound, for example, observations in Czechia associated with Tohoku 2011, Nepal 2015 or Turkey 2023 earthquakes. It is also shown that only long period waves (around 3 min) from the initial wave spectrum were able to reach such a high altitude. The initial wave spectrum of vertical ground surface motion that generated the infrasound waves was much broader, including more intense fluctuations at periods around 20 s, but these shorter period waves were attenuated below the altitude of observation. The observation is consistent with numerical simulations of infrasound propagation.
How to cite: Chum, J., Base, J., Mosna, Z., and Zednik, J.: Ionospheric perturbations over central Europe caused by the Kamchatka M8.8 earthquake on 29 July 2025. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5250, https://doi.org/10.5194/egusphere-egu26-5250, 2026.
The G5-class geomagnetic storm of 10–11 May 2024 produced one of the most extreme space-weather disturbances of Solar Cycle 25, generating large-scale perturbations across the thermosphere–ionosphere system. Over the Indian dip equatorial station Trivandrum (8.5°N, 76.9°E), the storm caused unusually strong enhancements in daytime Vertical Total Electron Content (VTEC) accompanied by distinctive, short-period undulations in electron density. These signatures reveal the strong and often competing roles of storm-time electric fields and thermospheric neutral winds in regulating equatorial plasma dynamics. Understanding their coupled influence is essential for advancing upper-atmosphere physics and improving global space-weather prediction.
In this study, we examine the ionospheric response to the May 2024 Great storm using multi-instrument observations and a physics-based equatorial and low-latitude ionospheric model. Observational datasets include GNSS-derived VTEC, DPS-4D Digisonde electron density profiles and ionospheric electron content (IEC), and high-resolution interplanetary and geomagnetic parameters. Storm-time meridional neutral winds are obtained from AMIE-constrained TIEGCM simulations, while vertical plasma drifts are specified using a prompt-penetration electric field (PPEF) model that maps solar-wind electric fields into the equatorial ionosphere.
To isolate the physical drivers, four controlled model experiments were conducted: (1) quiet-time winds with quiet-time drifts; (2) storm-time PPEF drifts with quiet winds; (3) storm-time winds with quiet-time drifts; and (4) storm-time forcing combining both PPEF and disturbed winds. This approach allows a clear separation of electrodynamic and thermospheric contributions to storm-time plasma redistribution.
The simulations show that PPEF-driven uplift dominates the overall magnitude of the TEC enhancement, raising the F-region peak and increasing the integrated electron content. However, the observed short-period VTEC and density undulations emerge exclusively when storm-time meridional winds are imposed. These winds undergo rapid reversals between poleward and equatorward directions, driven by high-latitude Joule heating and changes in thermospheric circulation. The resulting modulation of field-aligned diffusion produces alternating enhancements and depletions in plasma density, closely matching the temporal structure seen in Digisonde profiles and GNSS VTEC.
The combined PPEF + disturbed wind simulation reproduces the pre-noon features. In the afternoon sector, however, both model and Digisonde underestimate GPS VTEC, indicating a substantial contribution from the plasmasphere above 1000 km, consistent with observed F3 layer signatures. This highlights the importance of including ionosphere–plasmasphere coupling in models aimed at predicting low-latitude storm responses.
Our results provide the first detailed evidence from the Indian sector that rapid meridional wind variability can imprint strong, short-timescale signatures on equatorial electron density during an extreme geomagnetic storm. They demonstrate that neutral winds and electric fields are jointly responsible for shaping storm-time equatorial ionospheric structure, underscoring the need for coupled thermosphere–ionosphere–plasmasphere modeling frameworks.
How to cite: Ashok, A., Kailasam Madathil, A., and Choudhary, R. K.: Neutral Wind–Electric Field Coupling in the Equatorial Ionosphere During the May 2024 Great storm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-802, https://doi.org/10.5194/egusphere-egu26-802, 2026.
Quiet geomagnetic conditions provide a unique window into ionospheric dynamics driven by lower-atmospheric forcing and weak background magnetospheric coupling. By applying Faraday rotation rate–based methods to transionospheric HF radio-wave polarization measurements from the Radio Receiver Instrument (RRI) on Swarm-E/e-POP, differential total electron content (dTEC) in the ionosphere can be derived at substantially higher along-track resolution than provided by GPS. In this work, dTEC observations from GPS and RRI during two geomagnetically quiet days in December 2017 are examined in order to characterize background ionospheric dynamics under weak magnetospheric forcing. Similar large-scale wavelike structures observed on consecutive days by both RRI and GPS indicate persistent regional density perturbations. Additionally, RRI resolves small-scale (7 to 50 km) dTEC variations with amplitudes of ±1 to 2 TECU that are not captured by GPS. Repetitive enhancements and depletions confined to narrow latitudinal bands of about 0.25°, corresponding to roughly 25 km, indicate a quiet-time ionosphere structured by continuous mesoscale and small-scale forcing. This is consistent with upward-propagating disturbances from the lower atmosphere that are associated vertical coupling with the ionosphere.
How to cite: Kalafatoglu Eyiguler, E. C., Hussey, G. C., Danskin, D. W., Gillies, R. G., Burrell, A. G., Coster, A. J., Pandey, K., and Yau, A. W.: Quiet-time ionospheric density variations observed by the Radio Receiver Instrument on e-POP/Swarm-E, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8198, https://doi.org/10.5194/egusphere-egu26-8198, 2026.
This study investigates the occurrence, characteristics, and formation mechanisms of slant sporadic-E layers (Ess). The Ess-type layers observed at the Brazilian low-latitude stations of Jataí (17.9°S, 51.7°W) and São José dos Campos (23.2°S, 45.8°W), are analyzed using ionosonde data recorded for four months (April, June, September, and December) of 2016. Parameters such as top frequency (ftEs), blanketing frequency (fbEs), and virtual height (h’Es) were scaled from ionograms to characterize the slant (Ess) traces. The results show that Ess-type layers predominantly occur at night, forming between 95 and 120 km altitudes, with monthly and local variations. Model simulations using meteor radar-derived winds revealed that strong and stable zonal wind shear are associated with increased Ess-type layer activity. In addition, wavelet spectral analyses of ftEs and fbEs showed that tidal periodicities (diurnal, semidiurnal, terdiurnal, and quarterdiurnal) and their interactions with gravity waves seem to play fundamental roles in the formation of Ess-type layers. A comparison of ΔF (ftEs-fbEs) during Ess-type events confirmed the presence of strong plasma density gradients, supporting the hypothesis that the slanted traces in ionograms result mostly from oblique reflections in inhomogeneous Es layer structures. However, the appearance of slant Es traces may in some cases be related to an actual tilt of the layer. Other relevant aspects of the observations associated with the possible physical mechanisms behind the formation of Ess-type layers at low latitudes are highlighted and discussed
How to cite: Muka, P. T., TAH Muella, M., Conceição-Santos, F., Resende, L. C., Fagundes, P. R., Loius Ogunmola, O., Fontes, P., Gil Pillat, V., Cesar, M., and de Jesus, R.: Characteristics of slant sporadic-E layers observed at low-latitudes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2153, https://doi.org/10.5194/egusphere-egu26-2153, 2026.
METAL is one of 11 proposals that have passed the preliminary evaluation in the "test call" of ESA mini-F (only 50 Meur with 10-20 kg payload at LEO). The METAL mission aims to measure metallic (non-volatile) ions in the upper ionosphere of the Earth, both below and above the exobase, to address the overlooked basic questions for the first time:
(Q1) How are metallic ions, the best tracer in the ionosphere, lifted up in various conditions?
(Q2) How much is the ionosphere polluted by ablated anthropogenic metallic ions originating from space waste?
Only one or two ion instruments (ion mass spectrometer covering m>70, and mass-resolving ion energy spectrometer covering up to 100 eV) on board high-inclination LEO (<300 km times >500 km, ideally 1000 km) are needed, making the mission cost very low. The required specification of the mass spectrometer is already available, by which more sciences such as
(q3) How localized is the ionization chemistry in latitude?
can be performed.
While Q1 and q3 are related to basic ionospheric science (both physics and chemistry), Q2 is related to anthropogenic environmental issue that requires prompt measurements rather than comprehensive measurements: pollution of the upper atmosphere by re-entering space waste (launch vehicle, used satellites, and space debris). Since a substantial fraction of the re-entering space waste burn up (=ablated) in the upper atmosphere, and since the composition of the space waste is quite different from those of meteoroids, some elements (Li, Al, Cu, Ge, Pb) are already fully polluted compared to the natural origin.
Some of these ablated atoms are expected to be accumulated near the ionopause (metallic layer) in the same mechanism as natural process through meteor ablation, and some (although small fraction) of accumulated metals are lifted up (after ionization) to the ionosphere and magnetosphere, as are the natural metallic ions. Considering the difficulty of regular measurement in the mesosphere and lower ionosphere (to high for balloons and too low for satellites), in-situ measurement by satellites, even about 300 km altitude, is one of the best method to diagnose the anthropogenic contamination of the mesosphere.
How to cite: Yamauchi, M. and the The METAL proposal team: METAL proposal for ESA mini-F mission: How do natural and anthropogenic metallic ions access the geospace?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6263, https://doi.org/10.5194/egusphere-egu26-6263, 2026.
The Earth’s ionosphere can be driven by the Sun, the solar wind, the magnetosphere, as well as the neutral atmosphere. These drivers influence the ionosphere on a variety of spatial and temporal scales. The ionosphere is highly dependent on the driving processes and is highly dynamic. Modelling this plasma and capturing its full dynamic range is challenging.
Swarm is the European Space Agency’s (ESA) first constellation mission for Earth Observation (EO), comprising multiple satellites in Low Earth Orbit (LEO). Numerous data products are available, including measures of the ionosphere at a range of spatial scales. During the Swarm-VIP-Dynamic project, which ended in February 2026, the technique of Generalised Linear Modelling was used to create a suite of statistical models. These models predict the electron density and the variability in the ionospheric plasma at spatial scales between 100 km and 7.5 km. The models were based upon proxies for the heliogeophysical processes, as well as measurements of the thermosphere and ionospheric current systems. In addition to the Swarm data, datasets from other satellites and ground-based instruments were used for model evaluation and validation activities.
The performance of the models of the electron density approached the theoretical best values for some of the goodness-of-fit statistics that were to evaluate these models. This suggests that the modelling method is appropriate for the task undertaken. The models of ionospheric variability at larger spatial scales (~100 km) also performed well, however the model performance decreased at smaller spatial scales. This suggested that there is a physical process missing from the models. Possible candidates are instability processes or driving of the ionosphere by wave activity from below, neither of which are captured by the models at present. It is possible to test whether atmospheric waves originating in the lower atmosphere are driving the variability at European midlatitudes using different proxies for wave activity, and the ways in which this could be tested are discussed.
How to cite: Wood, A., Kotova, D., Doornbos, E., Urbář, J., Spogli, L., Jin, Y., Alfonsi, L., Dorrian, G., Hoque, M., van Dam, K., and Miloch, W.: Statistical Models of Ionospheric Variability and Irregularities in the Topside Ionosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10171, https://doi.org/10.5194/egusphere-egu26-10171, 2026.
To reach predictive capabilities in the future and to be able to evaluate the consequences of extreme events, it is of utmost importance to understand the interrelated processes in the Earth’s Magnetosphere, Ionosphere, Plasmasphere, and Thermosphere (MIPT).
Such a coupled system requires a complex approach, and the coupling processes between these different systems need to be better understood and quantified. Historically these subsystems of the near-Earth space environment are considered in isolation, as research in these highly related disciplines is separated by the traditional boundaries of universities that assign these areas to atmospheric sciences, geodesy, or physics and astronomy, depending on the distance from the Earth. Additionally, these research areas are allocated to different sections of the European Geosciences Union (EGU), the American Geophysical Union (AGU), and the International Association of Geodesy (IAG). Scientists who study subjects such as the thermosphere and magnetosphere rarely overlap in topical meetings, receive support for joint projects, or have a chance to collaborate. The main focus of the MIPT multidisciplinary Research Unit (RU) is to form this collaborative network, providing the impetus to achieve a better understanding of the various coupling and feedback mechanisms in the upper atmosphere and near-Earth space , and to understand how this complex system is driven by solar activity.
How to cite: Shprits, Y.: Magnetosphere, Ionosphere, Plasmasphere and Thermosphere, as a coupled system DFG Research Unit, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14517, https://doi.org/10.5194/egusphere-egu26-14517, 2026.
The Earth's Magnetosphere-Ionosphere-Thermosphere (MIT) system is strongly
controlled by the laws of electrodynamics, which include significant contributions from all three
components.
Today, we face a growing need for a better representation of this MIT system, at all latitudes due to
the growing use of GNSS satellites for positioning, which face accuracy and forecasting challenges
that are not accessible with current data coverage and processing tools.
The IRAP Plasmasphere-Ionosphere Model (IPIM) is one of the only physical models developped
in Europe which solves plasma transport equation along magnetic field lines and provides a
complete 3D coverage of Earth's ionosphere and plasmasphere in latitudes, longitudes and altitudes.
The model is suited to study the high latitude ionosphere, but some adjustement has to be done on
the inputs in order to simulate geomagnetic disturbances.
Thus, we will present the model and some interesting results at high latitudes for geomagnetic events.
How to cite: Resseguier, A., Blelly, P.-L., and Marchaudon, A.: Modeling the high-latitude MIT system with the IPIM model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21252, https://doi.org/10.5194/egusphere-egu26-21252, 2026.
The Graz University of Technology processes thermospheric neutral densities for several satellite missions, primarily using GNSS observations (SWARM, TerraSAR-X, Sentinel etc.) and accelerometer measurements (CHAMP, GRACE, GRACE-FO). However, before accelerometer measurements can be used for this purpose, they must be calibrated. Until recently, we used the already established calibration scheme from gravity field recovery to also estimate densities. These two calibration schemes are now independent of each other. Since our last release, we have updated the satellite force modeling, unified some parametrizations and introduced a variable molecular mass to account for the thermosphere's dependence on the solar cycle. All of these changes are included in our new release.
Currently, combining all estimation techniques yields a dataset spanning approximately 25 years. This dataset is a potent tool for studying the impact of space weather. During this period, numerous geoeffective CMEs occurred, as is clearly visible in the density time series. This study emphasizes the effects of recent severe solar storms. We present these extreme events and contextualize them within the last two solar cycles. To support further research, we explain our publishing scheme and provide download links.
How to cite: Strasser, A., Krauss, S., Temmer, M., Dumitraschkewitz, P., Öhlinger, F., and Mayer-Gürr, T.: Satellite Based Neutral Densities and Their Application to Solar Storm Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18168, https://doi.org/10.5194/egusphere-egu26-18168, 2026.
The rapidly increasing population of active satellites and space debris in Low Earth Orbit (LEO) means that accurate and precise orbit prediction is becoming ever more important to avoid catastrophic collisions. Atmospheric drag is the second largest force on objects in LEO after gravity, and so orbit prediction requires models of the thermosphere that can predict the variations in density that directly affect atmospheric drag. The most popular physics-based global circulation models (GCMs) have chosen different upper boundary heights, ranging between 400-800 km for quiet-moderate activity levels. Yet orbit perturbations by atmospheric drag have been observed at much higher heights. How realistic is it to extrapolate densities above the boundaries of fluid models to altitudes that are notoriously poorly observed, and where particle trajectories are presumed ballistic? Furthermore, how well are we capturing the coupling of the ionosphere, magnetosphere and lower atmosphere? The thermosphere’s upper boundary is very susceptible to space weather and can rise by a few hundred km within a few hours in response to a sudden storm commencement and Joule heating, right into the path of a LEO satellite. Climate change is also causing the upper boundary to move down over long timescales, which is due to the cooling and contraction of the stratosphere, mesosphere and lower thermosphere in response to increasing CO2 levels.
We propose that one way to identify and estimate the top of the thermosphere is by monitoring objects in free-fall. We look at 38 Cubesats from the QB50 mission over their lifetime of 2017–2025, covering solar minimum and maximum; and at the whole catalogue of over 20,000 LEO satellites during the Gannon Superstorm of May 2024. In particular, we find that the “top of the thermosphere”, as evidenced by atmospheric drag, depends on the orbiting body, as well as space weather and climate change.
How to cite: Aruliah, A., Aguilar, L., Dable, E., Constant, C., Bhattarai, S., Balkanski, A., and Cnossen, I.: Where is the top of the thermosphere? And why it matters., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7662, https://doi.org/10.5194/egusphere-egu26-7662, 2026.
The dynamics of the ionosphere and plasmasphere are strongly coupled: the ionosphere refills the plasmasphere on the dayside, while plasmaspheric particles help sustain the ionosphere at night. The NeQuick model, for instance, extrapolates ionospheric dynamics into the plasmasphere using parameters anchored in the F2-layer. However, despite these strong coupling processes, empirical models can benefit from treating these "spheres" as distinct regions. In this work, we propose a new formulation for the NeQuick model, which considers the plasmasphere as a layer entirely independent of ionospheric parameters. This adjustment led to significant improvements, partially resolving previous model underestimations and preserving a more realistic plasmaspheric structure along geomagnetic field lines. Based on extensive validation using data from 2008 to 2024, the revised NeQuick model demonstrated improvements ranging from 28% to 40%, depending on solar activity. These results suggest that modeling the ionosphere and plasmasphere as independent layers is a viable solution for improving both accuracy and the representation of plasma structures.
How to cite: Prol, F., Pignalberi, A., and Smirnov, A.: Improving NeQuick Model Connection between the Topside Ionosphere and Plasmasphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13727, https://doi.org/10.5194/egusphere-egu26-13727, 2026.
The ionosphere plays an important role for the propagation of radio signals. The majority of ionospheric disturbances is caused by magnetospheric and solar processes. However, a significant number of disturbances cannot be explained by these external forcing mechanisms. It is suspected that internal atmospheric dynamics, including small- and large-scale waves propagating from the lower atmosphere into the ionosphere, are the cause of much of the remaining variability (e.g., the formation of sporadic E-layers).
These ionospheric disturbances are a significant and highly variable source of positioning errors of global navigation satellite system (GNSS) signals. The relation between middle atmospheric dynamics and GNSS signal integrity is studied by utilizing several years of OH airglow observations in the vicinity of European Geostationary Navigation Overlay Service (EGNOS) grid points.
OH airglow observations provide neutral atmospheric temperatures at the upper mesosphere lower thermosphere (UMLT), i.e. at approximately 80 to 100 kilometers height, so in the ionospheric D region. Ground-based airglow observations with high temporal resolution are performed at the reference site of the Network for the Detection of Mesospheric Change (NDMC) at the Environmental Research Station Schneefernerhaus (UFS, 11.0° N, 47.0° E) since 2009. These data allow precise observations of acoustic, gravity, tidal and planetary wave disturbances in the UMLT; at least some of these atmospheric waves can propagate from the D region higher up into the E region or maybe F region.
While the EGNOS provides integrated information on the ionospheric state at a given time, the OH airglow at the lower edge of the ionosphere is influenced amongst others by upward propagating phenomena. Therefore, we investigate the relationship between EGNOS-broadcasted ionospheric delays and observed UMLT-variability addressing the question whether airglow observations can be used to perform short-term predictions of GNSS signal deterioration by atmospheric variability. Emphasize is placed on the role of semi-diurnal tides and a potential connection to a semi-annual oscillation observed in EGNOS-delay information.
How to cite: Abbes, M., Schmidt, C., Wüst, S., Goussev, O., and Bittner, M.: Investigation of a potential correlation between OH nightglow variability and GNSS/EGNOS Integrity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11389, https://doi.org/10.5194/egusphere-egu26-11389, 2026.
The Tongue of Ionization (TOI) is the typical ionospheric irregularity in the polar region. During the superstorm on 10 May 2024, an unexpected altitudinal discrepancy of TOI in the Southern Hemisphere is observed. Three-dimensional Computerized Ionospheric Tomography (3DCIT) results show that between 21:30 and 22:30 UT, the TOI decays at 500 km while simultaneously expands at 800 km, exhibiting a contrasting vertical evolution that has not been previously reported. Simulations reveal that the dayside upward E×B drift produce the higher density in SED region in the top ionosphere. Then, at 800 km, more plasma is moved into the polar region, forming the stronger TOI. Beyond the commonly emphasized dayside E×B drift transport, nightside meridional winds also play a crucial role in generating the altitudinal discrepancies. Strong equatorward winds uplift plasma along the geomagnetic field lines and supplied sufficient plasma to maintain the TOI structure during nighttime in the top ionosphere.
How to cite: Zhai, C.: Strong Altitudinal Discrepancies in the Polar Tongue of Ionization During the Super Geomagnetic Storm on 10 May 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2043, https://doi.org/10.5194/egusphere-egu26-2043, 2026.
Solar wind–driven disturbances excite Alfvénic perturbations in the Earth’s magnetosphere that propagate along geomagnetic field lines toward Earth, with the ionosphere being the inner boundary where field-aligned currents close. Horizontal gradients in the Hall and Pedersen conductances have previously been invoked to explain rotations of the convection pattern in response to magnetospheric forcing (Lotko et al., 2014).
We employ a time-dependent 2D model of the ionosphere driven by the magnetosphere. The radial magnetic field perturbations are generated inductively, numerically solving the induction equation along with the two-fluid equations, allowing us to capture the gradual formation of the convection pattern and to understand the role of the ionization/recombination processes or pressure gradients.
We investigate the temporal evolution of the system under a range of realistic and hypothetical high-latitude Hall and Pedersen conductance distributions. We find that gradients in either Hall or Pedersen conductance can alter the convection pattern, in contrast to earlier results suggesting that only Hall conductance gradients play a role.
How to cite: Popescu Braileanu, B., M. Laundal, K., and M. Hatch, S.: The role of Hall and Pedersen conductivity profiles in the ionospheric response to magnetospheric driving, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14069, https://doi.org/10.5194/egusphere-egu26-14069, 2026.
Alfvén waves with small perpendicular scale lengths are dispersive and can carry parallel electric fields. In the Earth's magnetosphere, they capture and accelerate electrons in a resonant process along the magnetic field lines down into the high-latitude ionosphere. These wave-particle interactions are considered to be a significant driver of auroral particle acceleration and as such an important coupling process between the magnetospheric and ionospheric systems. However, studying these waves and their associated auroral precipitations remains challenging due to the short temporal and spatial scales involved. As a result, their role in auroral dynamics continues to be an active area of research.
Here, we present data from one of the VISIONS-2 (Visualizing Ion Outflow via Neutral Atom Sensing-2) sounding rocket launched in December 2018 from Ny-Ålesund, Svalbard, in the active dayside auroral region. Numerous time-energy dispersed structures, indicative of particle acceleration by Alfvén waves, were observed by the top-hat ESA instrument. We present the high-resolution measurements of several of these structures and analyse their time-of-arrival in energy and pitch-angle. We discuss the implications of these observations for understanding the acceleration region.
How to cite: Gavazzi, E., Spicher, A., Gustavsson, B., Clemmons, J., and Rowland, D.: Auroral electron acceleration by dispersive Alfvén waves – insights from the VISIONS-2 rocket mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19919, https://doi.org/10.5194/egusphere-egu26-19919, 2026.
Omega bands are an auroral structure which consist of upward and downward field aligned currents (FACs) which are formed in the boundary between the region 1 and region 2 FACs in the dawn sector. They are characterised by their wave-like structure, which is often described as looking like a chain of the Greek letter Ω, with luminous extensions of the aurora protruding poleward. Omega bands cause ground based perturbations as they drift eastward, which can have large dB/dt values and hence are a potential source of geomagnetically induced currents (GICs). GICs are a hazard to our infrastructure, as currents can be induced in power grids, railways and pipelines. In this study, we investigate several cases of omega bands using ground and spaced based observations to examine their properties. Observations from the European Incoherent SCATter (EISCAT) radar show enhancements in electron density, which alongside measurements of FACs from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) can be used to study the intensity of different events. We use the IMAGE magnetometer network across Scandinavia to explore the latitudinal extend of omega bands as well as see their drift speed and dB/dt strength. SuperDARN and DMSP ion drift meter measurements help us to determine if the omega bands are embedded in the convection flow. Data from the DMSP Special Sensor Ultraviolet Spectrographic Imager (SSUSI) show the auroral data associated with omega bands. We present a study of omega bands from 2010 onwards.
How to cite: Hodnett, R., Milan, S., Gjerloev, J., Vines, S., Paxton, L., Nozawa, S., and Raita, T.: Omega bands as a source of dB/dt in the auroral dawn sector, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20143, https://doi.org/10.5194/egusphere-egu26-20143, 2026.
This paper presents GNSS radio occultation (RO) observational analyses on deducing the relationships and dependences between post-sunset EPB occurrences and EIA strength variability. The RO data were acquired from the FS7/COSMIC2 Program from 2020 to 2025. In this study, we incorporate both effects from crest peak electron density (Nemax) and crest-to-trough Nemax ratio and propose a new EIA strength parameter defined as the mean of northern and southern crest-to-trough Nemax differences to recognize and characterize the post-sunset EIA features. Both seasonal–longitudinal appearances of intense post-sunset EPB occurrences and strong EIA events occurred on more or less 30 days expanded from when and where magnetic flux tubes align with the sunset terminator at the magnetic equator but have more intense EPB and/or strong EIA days during southern (northern) hemispheric summers in the South American area (the Central Pacific area and the Africa area). It is well consistent with Tsunoda’s hypothesis during the evening pre-reversal enhancement (PRE) and reveals more informationt on day-to-day variability, intensities and extents of post-sunset EPB occurrences and EIAs subject to seasonal, longitudinal, and solar cycle variability. Moreover, the local-time evolutions of peak post-sunset EIAs occurred during 19~20 LT which is earlier than that of the obtained experimental peak (i.e., 20:20 LT) of post-sunset EPB occurrences. We expect that the post-sunset EIA detection could be a potential precursor for post-sunset EPB occurrence.
How to cite: Tsai, L.-C., Su, S.-Y., Lv, J.-X., Schuh, H., Alizadeh, M. M., and Wickert, J.: Evolution of post-sunset equatorial plasma bubbles: relationships to the equatorial ionospheric anomaly induced by pre-reversal enhancement electric fields, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-474, https://doi.org/10.5194/egusphere-egu26-474, 2026.
An automatic scheme to detect equatorial plasma bubbles had been developed for Ionospheric Plasma and Electrodynamics Instrument (IPEI) onboard ROCSAT-1 satellite which was in a 35° inclination orbit at 600 km altitude (Su et al., 2006). However, some mis-identifications could be found in the southern hemisphere of the negative magnetic declination longitudinal region during June solstice when the scheme was applied for data measured by Advanced Ionospheric Probe (AIP) onboard the FORMOSAT-5 satellite which was in a 98.28° inclination sun-synchronous circular orbit at 720 km altitude. The mis-identifications seems to relate to mid-latitude ring ionospheric troughs (Karpachev, 2019). In this presentation, global seasonal patterns of the equatorial plasma bubbles from FORMOSAT-5/AIP data during 2018 to 2025 were re-generated by a revised scheme like the rate of change of density index (RODI) by Jin et al. (2019) and are similar to the patterns obtained by ROCSAT1/IPEI data during 1999-2003.
How to cite: Chao, C.-K.: A Revised Automatic Detection Scheme to Identify Equatorial Plasma Bubbles Observed by Advanced Ionospheric Probe Onboard FORMOSAT-5 Satellite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4198, https://doi.org/10.5194/egusphere-egu26-4198, 2026.
Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) is used to investigate underlying physical processes of the thermospheric and ionospheric vortex-like structure over East Asia region in November 2003 superstorm. Horizontal neutral winds with a vortex configuration modulate the composition (O/N2) perturbations, forming the two-dimensional vortex-like structure. Vertical winds also have a positive contribution to the final shape of this structure in the altitude distribution. The ionospheric vortex-like structure below the ionospheric peak height (hmF2) is dominated by chemical effects (O/N2 enhancements) and neutral wind transport, while it is directly controlled by the neutral wind transport above the hmF2. Decreases of plasma density within the core region of this structure, driven by E×B drifts at all altitudes, also contribute to its formation. Analysis of the forcing terms driving the wind vortex in the middle thermosphere reveals the dominant role of pressure gradients, alongside the combined action from Coriolis force and horizontal momentum advection. In the upper thermosphere, the ion drag becomes significant, but only partially offsets the substantial positive effects of pressure gradients. Furthermore, controlled numerical experiments demonstrate that the storm intensity is not the single trigger mechanism for this structure. Instead, the asymmetrical prevailing circulation is more beneficial to the formation of the vortex-like structure. The storm onset time also affects the formation and location of this structure, although it is more liable to appear near the magnetic poles primarily in the American and East Asia sector.
How to cite: Yu, T., Zhao, B., Ren, Z., and Guo, X.: The underlying physical processes of the vortex-like structure over the East Asia region during the recovery phase of the November 2003 superstorm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17147, https://doi.org/10.5194/egusphere-egu26-17147, 2026.
The ionosphere is the ionized region of the atmosphere extending from 50 km to 1000 km. During solar flares, the near-Earth space environment is subjected to enhanced high-energy X-ray and EUV radiation, which significantly impacts ionospheric conditions. Variations in ionospheric parameters measured by ionosondes, specifically the fmin and foF2 values, were examined during solar flares occurring under geomagnetically quiet conditions (Dst > −40 nT, Kp < 4) between 2023 March and 2024 June . The required data were obtained from manually evaluated ionograms recorded by the Czech DPS4D ionosonde at Pruhonice (PQ052).
The degree of variation was determined by comparison with monthly mean values, allowing the calculation of deviations in the studied parameters (dfmin, dfoF2). Time series of these deviations were analysed. Furthermore, the relationship between the ionospheric deviations and a flare “geoeffectiveness” parameter was investigated. This parameter was defined by considering the X-ray flux, the solar zenith angle at the station at the time of the event, and the position of the flare on the solar disk. A positive correlation was found between dfmin and the flare geoeffectiveness parameter, which proved to be stronger than the correlation obtained for dfoF2. In addition, a cumulative dfmin parameter was introduced, and its correlation with integrated X-ray flux values was examined. In this case as well, the flares were separated by intensity classes, similarly to the non-integrated analysis. The strongest correlation was obtained for flares above M6, reaching a maximum correlation coefficient of 0.97.
The relationship between EUV radiation and the ionospheric parameters was also investigated; however, these correlations were found to be considerably weaker and did not reach comparable levels of statistical significance.
How to cite: Erdey, J., Barta, V., Buzás, A., and Lichtenberger, J.: The Impact of Solar Flares on the Ionosphere During Geomagnetically Quiet Periods, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14193, https://doi.org/10.5194/egusphere-egu26-14193, 2026.
Space weather events such as solar flares and energetic particle events cause enhanced absorption of radio waves in the lower ionosphere, posing difficulties to radio communication at certain frequencies. Increases in ionospheric absorption are due to enhancement of the ionisation in the D region which can be related to the following sources: (1) increases in hard X-rays during solar flares, which affects the day-lit side of the earth especially at lower latitudes, (2) impacts by high-energy solar protons, which can reach the D region in the polar cap were the field lines of the geomagnetic field are open , and (3) precipitation of electrons due to recombination events in the magnetotail, which can produce D-region ionisation in the auroral oval region.
Determination of the changes in ionospheric absorption is possible using ionosounding techniques in which the ionosonde actively emits radio pulses towards the ionosphere over a selected frequency sweep (typically between 1.5 and 14 MHz), and the passive antenna system of the same instrument receives the reflected echoes. The absorption can be defined by the minimum frequency reflected by the ionosphere what can be recorded on the ionograms (fmin parameter, Barta el a. 2019). It can also be quantified based on the received amplitudes of the echoes (Buzás et al. 2023). An alternative approach to analyze the signal-to-noise ratio of radio waves recorded on ionograms during solar events (de Paula et al. 2022). Another method to determine the absorption variation is to use the instrument in "listening mode" and analyze the background noise observed in the HF band (practically in 10–30 MHz range) during solar events.
The main purpose of the current study is to investigate the ionospheric absorption changes over Europe during the Mother’s Day Superstorm, determined from different type of data recorded by ionosondes at midlatitudes. A detailed analysis of the probable sources of the absorption changes —solar flare effects, polar cap and/or auroral absorption— will be discussed. Furthermore, we will compare the advantages and disadvantages of the different methods based on the results.
References:
Barta, V., Sátori, G., Berényi, K. A., Kis, Á., & Williams, E. (2019). Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa. Ann. Geophys. 37, 747-761. https://doi.org/10.5194/angeo-37-747-2019.
Buzás, A., Kouba, D., Mielich, J., Burešová, D., Mošna, Z., Koucká Knížová, P., & Barta, V. (2023). Investigating the effect of large solar flares on the ionosphere based on novel Digisonde data comparing three different methods. Front. Astron. Space Sci., 10:1201625. https://doi.org/10.3389/fspas.2023.1201625.
de Paula, V., Segarra, A., Altadill, D., Curto, J. J., & Blanch, E. (2022). Detection of solar flares from the analysis of signal-to-noise ratio recorded by Digisonde at mid-latitudes. Remote Sens., 14, 1898. https://doi.org/10.3390/rs14081898.
How to cite: Barta, V., Verhulst, T., Altadill, D., Mosna, Z., Segarra, A., Szárnya, C., de Paula, V., and Buzás, A.: Ionospheric absorption variation during the Mother Day Superstorm in May 2024 as observed by different types of ionosonde data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9555, https://doi.org/10.5194/egusphere-egu26-9555, 2026.
- Magnetosphere-Ionosphere-Thermosphere coupling response to the 1st December 2023 geomagnetic storm at low- and middle-latitude regions
Syed Faizan Haider1*
1* Space Education and GNSS Lab, National Center of GIS & Space Applications, Department of Space Science, Institute of Space Technology, Islamabad 44000, Pakistan
Faizanhaider92110@gmail.com
Abstract:
We investigate the global effects of the December 1, 2023 geomagnetic storm on the magnetosphere, ionosphere and thermosphere by utilizing data from the Magnetometer, Global Navigation Satellite System (GNSS), Swarm Mission and Global Ultraviolet Imager (GUVI). We found distinct vTEC patterns across different latitudes during various storm phases. Stations in Asia, Africa, North America, and Central America showed vTEC peaks during the main phase. In contrast, stations at mid-latitudes demonstrated both positive and negative ionosphere storms. These variations are attributed to changes in the Prompt Penetration Electric Field (PPEF), influenced by oscillations in the Interplanetary Magnetic Field (IMF) Bz component and interactions with solar winds and Earth's magnetosphere. Moreover, both the meridional and zonal winds provided by Horizontal Wind Model 2014 (HWM14) displayed positive correlation with vTEC variations of multiple GNSS stations throughout the storm. This correlation was especially strong over the Asian stations during both the main and recovery phases, while stations in Africa, America, and Oceania showed more prominent correlations during the recovery phase. In addition, low latitude regions in Asia, as well as mid latitude regions in New Zealand, South Africa, and South America, all showed a negative ionosphere storm as a result of the modification of the thermosphere winds. Strong correlations between the Swarm satellite data, GNSS stations, and vTEC variations confirm storm-penetrated ionospheric disturbances. Furthermore, significant variations in Earth's magnetic field, including the H-component and Diono, are observed, highlighting the complex dynamics of ionospheric perturbations during geomagnetic storms across diverse latitudinal and longitudinal contexts.
Keywords: Ionosphere, Thermosphere, Magnetosphere, Geomagnetic Storm, GNSS, Remote Sensing, vTEC, PPEF, GUVI
How to cite: Haider, S. F.: Magnetosphere-Ionosphere-Thermosphere coupling response to the 1st December 2023 geomagnetic storm at low and middle latitude regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13708, https://doi.org/10.5194/egusphere-egu26-13708, 2026.
Understanding the variability of the thermosphere–ionosphere (T–I) system across different conditions is especially important, as its state critically affects the operation and safety of numerous low Earth orbit (LEO) satellites. In the absence of routine thermospheric monitoring, ionosonde measurements and satellite data can be used to retrieve key aeronomic parameters at mid-latitudes during noontime via the THERION (THERmospheric parameters from IONosonde observations) method.
This study applies the THERION technique to analyze the T–I response in the European and American longitudinal sector to two recent severe geomagnetic storms (October 2024 and January 2025). Validated ionosonde data from Rome, Juliusruh, Millstone Hill and Eglin were used to assess ionospheric variability and derive thermospheric parameters such as neutral composition, temperature, and wind. Results are compared with outputs from the MSISE00 empirical model, highlighting THERION's improved capability in capturing thermospheric dynamics under storm conditions.
Additional datasets—including co-located GNSS-derived TEC, geomagnetic field data from the INTERMAGNET network, and interplanetary/magnetospheric conditions—were integrated to provide a comprehensive view of the events and the unique T-I coupling processes associated with each storm.
This study is carried out within 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: Sabbagh, D., Perrone, L., Scotto, C., Ippolito, A., Spogli, L., Regi, M., and Bagiacchi, P.: Comparing Northern Hemisphere Mid-Latitude Thermosphere-Ionosphere Response to Two Recent Geomagnetic Storms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19800, https://doi.org/10.5194/egusphere-egu26-19800, 2026.
Anthropogenic greenhouse gas (GHG) emissions are the ongoing major driver of Earth’s climate change. While the increasing concentration of GHG causes a warming of the lower atmosphere, it leads to a cooling of the upper atmosphere, which is expected to result in a thermal contraction. These changes in the neutral atmosphere have been demonstrated to also influence the ionosphere. In fact, the contraction of the whole upper atmosphere should induce a downward displacement of the ionospheric layers due to the changes in the vertical distribution of the different ion species in the ionosphere.
To study the ionosphere changes in response to climate change, we investigate the long-term trends of the ionospheric equivalent slab thickness (τ). τ represents the thickness of an ideal ionospheric slab of constant electron density equal to that of the F2-layer peak (NmF2) with a vertical total electron content (vTEC) value equivalent to that of the entire ionosphere. To achieve this, we derive τ time series from a selection of globally distributed and co-located ionosondes (providing NmF2) and ground-based GNSS receivers (providing vTEC), focusing on stations with at least two solar cycles of continuous data. For trend and coherent structures extraction and analysis, we use the Empirical Mode Decomposition (EMD), an advanced data-adaptive decomposition method. EMD is particularly suited for preserving nonlinearity in time series and for processing non-stationary data, offering a more accurate representation of long-term variations compared to traditional statistical methods. We present preliminary results showing a global long-term decrease of τ, but with magnitudes dependent on latitude, pointing out a general shrinking of the ionosphere in the last two decades.
How to cite: Pignalberi, A. and Alberti, T.: Long-Term Trends in the Ionospheric Equivalent Slab Thickness: Is the ionosphere really shrinking?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5150, https://doi.org/10.5194/egusphere-egu26-5150, 2026.
Machine learning (ML) has shown growing promise for space weather applications. However, its performance is often limited by the scarcity of rare-event observations and a lack of physical consistency. In this study, we investigate plasmaspheric cold electron density modeling using approaches that span the spectrum from purely physics-based [1] to purely data-driven [4], with a focus on three hybrid physics–machine learning strategies. These strategies incorporate physical information through discrepancy correction, physics-informed input augmentation, and physics-based regularization. Each hybrid model combines density outputs from the VERB-CS [1] simulation with a neural network to estimate plasmaspheric cold electron density. The neural networks are trained using in situ electron density measurements from the Van Allen Probes [2] together with geomagnetic indices. Hybrid models embed key physical processes (such as particle transport, refilling, and loss mechanisms) into the learning framework.
We assess the predictive capability of the hybrid models relative to pure ML and pure physics-based approaches through comparisons with in situ Van Allen Probes observations and global plasmaspheric images from the IMAGE Extreme Ultraviolet instrument [3]. Our results indicate that the hybrid models reproduce both large-scale plasmaspheric structure and smaller-scale features more accurately than either purely data-driven or purely physics-based models across a range of geomagnetic activity levels. Incorporating physical information into the ML framework improves generalizability across different geophysical conditions, including periods of enhanced geomagnetic activity. These results demonstrate the potential of physics-informed machine learning approaches to advance predictive modeling of the near-Earth plasma environment.
References
[1] Aseev, N., Shprits, Y., 2019. Reanalysis of ring current electron phase space densities using Van Allen Probe observations, convection model, and log-normal Kalman filter. Space weather 17, 619–638.
[2] Kletzing, C., Kurth, W., Acuna, M., MacDowall, R., Torbert, R., Averkamp, T., Bodet, D., Bounds, S., Chutter, M., Connerney, J., et al., 2013. The electric and magnetic field instrument suite and integrated science (EMFISIS) on RBSP. Space Science Reviews 179, 127–181.
[3] Sandel, B., Goldstein, J., Gallagher, D., Spasojevic, M., 2003. Extreme ultraviolet imager observations of the structure and dynamics of the plasmasphere. Magnetospheric imaging—The image prime mission , 25–46.
[4] Zhelavskaya, I.S., Shprits, Y.Y., Spasojević, M., 2017. Empirical modeling of the plasmasphere dynamics using neural networks. Journal of Geophysical Research: Space Physics 122, 11–227.
How to cite: Shahsavani, S. and Shprits, Y.: Hybrid Physics–Machine Learning Modeling of Plasmaspheric Cold Electron Density, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3424, https://doi.org/10.5194/egusphere-egu26-3424, 2026.
Reliable modeling of plasmaspheric density during geomagnetically disturbed periods is limited by sparse in-situ observations at high geomagnetic activity. In this study, we extend the PINE (Plasma density in the Inner magnetosphere Neural network-based Empirical) model using a Physics-Informed Neural Network (PINN) framework to improve performance during extreme conditions (Kp > 6). Density predictions from the physics-based VERB-CS model are incorporated to augment training data for high-Kp events, addressing a key limitation of previous empirical approaches. We develop and evaluate two PINN-based models: one trained exclusively on high-Kp data and another trained on a combined data set including electron density measurements from the Van Allen Probes and Arase missions together with VERB-CS density outputs. The performance of these models is directly compared across geomagnetic activity levels, enabling a systematic assessment of the impact of physics-based data integration on plasmaspheric density predictions in terms of accuracy and error variance. Model outputs are also compared with independent IMAGE EUV observations to evaluate each model’s ability to reconstruct global plasmaspheric structures under disturbed conditions.
How to cite: Shilu, L., Shahsavani, S., and Shprits, Y.: Extending PINE for High-Kp Plasmaspheric Density Modeling Using Physics-Informed Neural Networks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18831, https://doi.org/10.5194/egusphere-egu26-18831, 2026.
The subauroral ionosphere is the transition zone between the convecting and corotating plasma and plays an important role in the magnetosphere - ionosphere (MI) interaction. The midlatitude ionospheric trough (MIT), a longitudinally extended depletion in electron density, is an important feature of this region. Various formation mechanisms have been proposed but some of their underlying physics remains unknown.
The MIT exhibits a strong dependence on magnetospheric activity and magnetic local time (MLT). This dependence has been captured by empirical models describing the location of the MIT (e.g., Deminov and Shubin, 2018; Werner and Prössl 1997).
In this study, we present a new empirical model that describes the location of the MIT electron density minimum and its associated equatorward and poleward walls. The model is based on empirical observations combined with ionospheric physics. The dataset is derived from the Swarm-PRISM MIT product (https://earth.esa.int/eogateway/activities/swarm-prism) where MIT features are identified using Langmuir probe measurements from the ESA Swarm mission. The model input parameters are MLT and a time weighted average of the geomagnetic activity represented by the Hp30 index (Yamazakiet et al., 2022). More than 170 000 of MIT events have been identified which is a large dataset compared to previous models allowing our model to provide a more precise and more featured description of the MIT compared to existing models. Our model can also provide a tool for monitoring magnetospheric processes and can advance the understanding of MIT formation mechanisms.
How to cite: Tomasik, M. and Heilig, B.: An Empirical Model of the Midlatitude Ionospheric Trough Based on Swarm Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21417, https://doi.org/10.5194/egusphere-egu26-21417, 2026.
Accurately estimating three-dimensional wind fields in the mesosphere and lower thermosphere (MLT) is crucial for understanding the dynamics and variability of the middle atmosphere, which exhibits complex behavior driven by a range of atmospheric waves covering spatial scales from kilometers to almost the diameter of the planet and temporal scales reaching from minutes to several days. Vertical winds are of particular interest and determine adiabatic heating/cooling as well as the vertical transport. They are challenging to retrieve due to their relatively weak magnitude compared to the horizontal wind components and instrument limitations. Multistatic meteor radar networks enable sophisticated tomographic wind retrievals, such as the Spherical Volume Velocity Processing (SVVP), or more advanced Bayesian methods like the 3DVAR+DIV algorithm. The current 3DVAR+DIV model is implemented in geographic and Cartesian grid coordinates based on pre-defined grid cells defined by a reference coordinate, which adversely affects the estimation of vertical winds due to the often low statistics and, thus, residual projection errors. The vertical winds are typically an order of magnitude weaker than horizontal winds and highly sensitive to even tiny projection errors.
In this study, we present the 3DVAR+DIV algorithm in spherical coordinates to account for the Earth’s curvature and the latitude-dependent change of the Earth’s radius. This implementation introduces several new unknowns per grid cell and will undergo multiple parameter tests using the Nordic Meteor Radar Cluster (NORDIC). This approach aims to improve the accuracy of wind retrievals, particularly for the vertical wind components. The new algorithm in spherical coordinates will mitigate the residual projection errors caused by the sparsity of the measurements.
How to cite: Poku, L. P., Stober, G., Krochin, W., Kozlovski, A., Lui, A., Janches, D., Tsutsumi, M., Gulbrandsen, N., Nozawa, S., Lester, M., Kero, J., Mitchell, N., and Yi, W.: Implementation of Spherical Coordinates in 3DVAR+DIV Model: An Enhancement of Geophysical Data Assimilation., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5625, https://doi.org/10.5194/egusphere-egu26-5625, 2026.
Stronger solar activity can modulate galactic cosmic rays reaching the Earth, affecting the production of Be-7 in the stratosphere and its subsequent downward transport. Corotating Interaction Regions (CIRs) and High-Speed Solar Wind Streams (HSSWS) significantly perturb the ionosphere, altering electric fields and plasma dynamics in the ionosphere, influencing Es layer formation and behavior. Often causing Es layer formation (higher electron density, stronger critical frequency) during geomagnetic disturbances.
We use radionuclide data (Be-7 in aerosols evaluated by the corresponding activity in aerosols on a weekly basis at the National Radiation Protection Institute Monitoring Section in Prague, Czechia) alongside ionospheric data (Es layers) to understand these interconnected space weather effects and atmospheric dynamics. Es layers, formed by dynamic processes, can influence atmospheric waves and vertical transport, potentially connecting upper atmosphere phenomena with atmospheric radionuclide levels in middle latitudes. The Be-7 concentrations are therefore a very promising indicator of the behavior of all atmospheric layers, including the mesospheric heights where the Es layer is located.
How to cite: Podolská, K., Šindelářová, T., Kozubek, M., Koucká Knížová, P., and Hýža, M.: Be-7 cosmogenic radionuclide concentrations as a tracer of dynamic processes in upper atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14769, https://doi.org/10.5194/egusphere-egu26-14769, 2026.
Spacecraft surface charging is one of the most common space environment effects and can pose significant risks to satellite operations through interactions with ambient plasma and space weather conditions. While spacecraft charging has been extensively investigated in high-altitude environments such as geostationary orbit (GEO), comparatively less attention has been given to low Earth orbit (LEO), where charging phenomena are often assumed to be less critical. However, the rapid expansion of the New Space sector and the increasing number of small satellites operating in LEO necessitate a renewed assessment of surface charging risks in this region. Despite this growing reliance on LEO, many small satellite manufacturers and operators still design and operate spacecraft with limited awareness of surface charging effects. In this study, we aim to provide scenario-based surface charging guidance applicable not only during the design phase of small satellite missions but, more importantly, for satellites already deployed and operating in LEO. Rather than performing precise, spacecraft-specific predictions, we construct a surface charging database based on generalized CubeSat-class geometries. The database is developed using the Spacecraft Plasma Interaction System (SPIS), a widely used numerical tool for spacecraft-plasma interaction analysis. Representative configurations commonly used in small satellite missions are considered, including 1U and 3U CubeSats, thin panel structures, and boom-equipped geometries. For each configuration, charging characteristics are evaluated across a range of surface material properties, latitude-dependent ionospheric plasma environments, and day–night illumination conditions.
The resulting database is not intended to deliver mission-specific absolute charging values. Instead, it provides qualitative and semi-quantitative information that enables satellite manufacturers and operators to assess whether an on-orbit spacecraft is likely operating under relatively benign charging conditions or exposed to potentially hazardous environments. This work helps bridge the gap between spacecraft charging physics and the practical operational needs of the CubeSat community, contributing to improved awareness of charging-related risks for small satellite missions in LEO.
How to cite: Na, G. W., Seon, J., Lee, D.-H., and Park, S. H.: Scenario-Based Surface Charging Guidance for CubeSat-Class Satellites in Low Earth Orbit, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16602, https://doi.org/10.5194/egusphere-egu26-16602, 2026.
ESA’s Sentinel program consists of multiple satellites for Earth observation. The first launches were in 2014; since then, the constellation has continued to grow. In this study, we will utilize Sentinel-1, Sentinel-2, Sentinel-3, and Sentinel-6. They all carry geodetic-type GNSS receivers, which are used for precise orbit determination, but in turn provide highly precise slant TEC observations. The satellites are located in altitudes between 730 km and 1350 km and can measure slant TEC between the receiver and GNSS satellites. This area is also the transition region from the ionosphere to the plasmasphere. Significant efforts have been made over the last few years to reliably connect the ionosphere and plasmasphere. The current IRI-2020 model provides multiple topside and plasmasphere options, recent works adjusted the NeQuick-2 model to better represent the plasmasphere, empirical electron density modeling for a combined ionosphere and plasmasphere, and even neural networks are successfully used. We investigate the performance of selected models by evaluating slant TEC differences between the observations from Sentinel and the models. Investigations are carried out for recent time spans starting in 2021, following the launch of Sentinel-6, including low and high solar activity, quiet and disturbed periods. To our knowledge, this study presents the first analysis of multi-GNSS TEC observations from Sentinel-6.
How to cite: Schreiter, L., Prol, F., Hoque, M. M., Smirnov, A., Milea, I.-A., and Schmidt, M.: Using Sentinel satellites for validation and quality assessment of topside ionosphere and plasmasphere models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18703, https://doi.org/10.5194/egusphere-egu26-18703, 2026.
Solar activity, including variations in solar radiation and transient disturbances in the solar wind, drives a variety of processes in Earth's atmosphere. Solar ultraviolet (UV) radiation provides the primary energy input to the mesosphere and lower thermosphere, while enhanced solar wind plasma and magnetic field variations can indirectly influence atmospheric dynamics through magnetospheric coupling. These processes lead to atmospheric emissions observed as airglow and, at higher latitudes, aurorae.
MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) provides an opportunity to study the mesospheric infrared O2 A-Band emission, whose variability and excitation mechanisms are not yet fully understood. Using MATS observations from February to May 2023, we extract time series of airglow brightness variations in the mesosphere. To characterize solar activity, we use solar UV flux measurements from NASA's SDO/EVE and TIMED/SEE instruments.
In addition, we examine the occurrence of coronal mass ejections and co-rotating interaction regions during the study period to assess their potential contribution to the observed variability. We present correlations between MATS airglow brightness, solar UV irradiance, and solar wind parameters to quantify the relative roles of radiative and geomagnetic drivers.
How to cite: Rausch, J., Blüthner, G., Temmer, M., Giono, G., Ivchenko, N., and Megner, L.: Solar UV flux in relation to airglow variability as seen by MATS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18805, https://doi.org/10.5194/egusphere-egu26-18805, 2026.
Due to the ionosphere's significant impact on radio signal propagation, accurate modeling and reconstructions of its electron density distribution are crucial for various applications involving trans-ionospheric signals, such as GNSS positioning, GNSS augmentation systems (e.g., EGNOS and WAAS), remote sensing, but also to enhance our understanding of ionospheric processes. Several approaches have been developed for ionospheric reconstruction by combination of actual observations with a physical or an empirical background model. When looking for storage space and runtime saving approaches, algebraic iterative methods have been used to ingest current measurements into background models, e.g. derivatives of the Algebraic Reconstruction Technique (e.g. ART, MART) and column-normalized methods (e.g. SART, SMART). Those methods are working without the modification of the model coefficients but by updating the background in the area surrounding the available current measurements.
We introduce the new 4D electron density reconstruction approach 4DSMART+ as a combination of SMART, the successive correction method and a time propagation model. We apply 4DSMART+ to reconstruct the electron density distribution within the topside ionosphere and plasmasphere on a global grid with altitudes between 430 and 20200 km for a 59-day period of the year 2015 with moderate ionospheric conditions. STEC measurements of eleven LEO satellites (e.g. Swarm, COSMIC-1, MetOp) are used as data base for the reconstructions where the NeQuick model serves as background.
The comparison of the reconstructions to assimilated STEC measurements shows consistency with a median error of 0.1 TECU and a standard deviation of 3.4 TECU. Furthermore, 4DSMART+ is compared to SMART+ and the NeQuick model with respect to its capability to reproduce independent STEC data from the three LEO satellites GRACE and Swarm A. The results show that 4DSMART+ decreases the median STEC error for GRACE and Swarm A STEC by up to ~84% and ~99%, respectively, compared to SMART+ and the NeQuick model. Validation by means of the COSMIC-1 radio occultation profiles shows that 4DSMART+ reduces the median of the relative residuals by up to 13% in comparison to SMART+ and the NeQuick model.
How to cite: Gerzen, T., Minkwitz, D., Schmidt, M., and Schreiter, L.: 4-D tomography method 4DSMART+ for the reconstruction of topside ionosphere and plasmasphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18373, https://doi.org/10.5194/egusphere-egu26-18373, 2026.
Active experiments in the ionosphere aim to artificially and significantly modify the space and/or ionospheric environment over large spatial scales. A typical goal of such experiment would be to deplete high energy particles from selected orbits, using, for example, physical processes based on wave-particle interactions with artificially emitted electromagnetic waves. In this work, we study electromagnetic waves generated by an electron beam in the ionosphere. We use the Beam Plasma Interaction Experiment (Beam PIE) as reference, with a typical altitude of ~500 km and a ~15 keV electron pulsed beam emitted parallel to the magnetic field. We rely on the heavily parallelized SMILEI code to perform a parametric study with fully kinetic Particle-In-Cell simulations of such beams. Such study is only made possible thanks to simulation cost reduction through a dimension reduction to a 2D problem with cylindrical symmetry. Varying both the main parameters of the beam (beam density, frequency, length, etc.) and of the ambient environment (magnetic field strength and cold plasma density), we investigate the impact of those parameters on the electromagnetic wave generation mechanism and the wave’s properties. We especially look into the dependance of the wave’s energy distribution and power to the initial beam properties.
How to cite: Dargent, J., Ripoll, J.-F., Beck, A., Chust, T., Belmont, G., Le Contel, O., Cerfolli, L., Farge, T., and Retinò, A.: Parametric study of the generation of electromagnetic waves in an active experiment with electron beams, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18083, https://doi.org/10.5194/egusphere-egu26-18083, 2026.
