Particle precipitation into planetary atmospheres is a key heliophysical process, controlled by solar wind, magnetospheric, and ionospheric interactions. At Earth, precipitation channels energy into the upper atmosphere, producing aurora, ionospheric currents, and enhanced satellite drag. These processes demonstrate the coupling of plasma regimes and their consequences for both natural variability and technological systems. This session emphasizes a system-science perspective on precipitation across a wide range of energies and impacts. We invite studies on the roles of different drivers, the spatiotemporal dynamics of solar wind structures and geomagnetic storms, and the effects on ionospheric conductivity, atmospheric chemistry, and dynamics.
Comparative studies of outer planet magnetospheres, shaped by unique but related drivers, further highlight universal coupling processes. We welcome theoretical, modeling, and observational contributions on the dynamics of inner magnetospheres at Earth and other planets, including magnetosphere–ionosphere coupling and responses to solar wind disturbances. Relevant datasets include MMS, THEMIS, Van Allen Probes, Arase, Cluster, LEO satellites, CubeSats, Juno, SuperDARN, magnetometers, optical imagers, incoherent scatter radars, and ground-based VLF measurements.
Accurate detector response modelling is essential for interpreting particle flux measurements in space radiation environments. Consequently, it improves the characterisation of the low-Earth-orbit radiation environment and enhances our understanding of particle dynamics within the South Atlantic Anomaly (SAA). In this work, we develop a high-fidelity response function for the Next Generation Radiation Monitor (NGRM) using Monte Carlo simulations within ESA’s GEANT4 Radiation Analysis for Space (GRAS) toolkit. We also parametrize the pitch angle distribution (PAD) as a sinnα function, aiming to convert the proton measurements from the Sentinel-6 spacecraft to omnidirectional fluxes. For comparison, we also implement a smoothed top-hat response function to quantify the uncertainties introduced by using simplified functions. High-resolution maps of the PAD exponent and the derived omnidirectional fluxes are produced to examine the spatial gradients within and around the SAA and to assess temporal variability. Particular attention is given to the newly formed proton belt that was observed after the intense magnetic superstorm of May 2024, which resulted in significant changes to the inner magnetospheric proton population.
How to cite: Christodoulou, E., Evans, H., Vuolo, M., Daglis, I. Α., Santin, G., and Nieminen, P.: Characterisation of the Newly Formed Proton Belt Following the May 2024 Geospace Magnetic Superstorm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-973, https://doi.org/10.5194/egusphere-egu26-973, 2026.
Space weather (SWE) strongly influences Earth’s atmospheric chemistry and climate. The young Sun, far more magnetically active than today, produced frequent and intense solar energetic particle (SEP) events that continuously bombarded Earth’s upper atmosphere. These high‑energy particles triggered chemical pathways capable of generating greenhouse gases such as CO, H₂, N₂O, and HCN [1–4].
Using a three‑model framework—a thermochemical–photochemical kinetics model [5,6], a radiative–convective model (EOS) [7], and an energy balance model (ESTM) [8,9]—we investigated how an extreme SWE event alters atmospheric composition and affects climate. Our goal was to test whether SEP‑driven chemistry could contribute to resolving the Faint Young Sun Paradox (FYSP), as suggested by Airapetian et al. [1].
SEP‑induced dissociation of N₂ produces N(²D), initiating chemical pathways that form N₂O, HCN, H₂, and CO. For Archean‑like atmospheres (90% N₂, 10% CO₂, with trace CH₄ or H₂), CO and H₂ are the dominant products, but the resulting surface warming does not exceed 0.3 K—insufficient to address the FYSP. Nitrogen‑bearing species contribute negligibly. Even enhancing SEP fluxes by an order of magnitude leaves atmospheric composition and climate response largely unchanged. Under modern atmospheric conditions, repeated Carrington‑like SEP events would instead cool Earth’s surface by ~4 K. These results indicate that although extreme space weather significantly alters atmospheric chemistry, its climatic impact remains too small to resolve the FYSP.
This work has recently been published in The Astrophysical Journal (ApJ) as Biasiotti et al. (2026), ApJ, 996, 93 [10].
References [1] Airapetian, V. S., Glocer, A., Gronoff, G., Hébrard, E., & Danchi, W. (2016). Nature Geoscience, 9, 452. [2] Solomon, S., Roble, R. G., & Crutzen, P. J. (1982). J. Geophys. Res., 87, 7206. [3] Solomon, S., Reid, G. C., Rusch, D. W., & Thomas, R. J. (1983). Geophys. Res. Lett., 10, 257. [4] Jackman, C. H., & McPeters, R. D. (2004). In Solar Variability and its Effects on Climate, Geophysical Monograph 141, 305. [5] Locci, D. et al. (2022). Planetary Science Journal, 3, 1. [6] Locci, D. et al. (2024). Planetary Science Journal, 5, 58. [7] Simonetti, P. et al. (2022). ApJ, 925, 105. [8] Vladilo, G. et al. (2015). ApJ, 804, 50. [9] Biasiotti, L. et al. (2022). MNRAS, 514, 5105–5125. [10] Biasiotti, L. et al. (2026). ApJ, 996, 93.
How to cite: Ivanovski, S., Biasiotti, L., Simonetti, P., Locci, D., Cecchi-Pestellini, C., Vladilo, G., Calderone, L., Dogo, F., and Monai, S.: How Extreme Space Weather Impact Earth’s Atmosphere and Climate: Exploring N₂O and the Faint Young Sun Paradox , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10516, 2026.
Plasmaspheric hiss plays an important role in radiation belt electron dynamics, and its excitation and propagation have long attracted attention. During a substorm, Van Allen Probe B observed the disappearance of plasmaspheric hiss at the magnetic dip, which was driven by the injection of energetic protons. The perpendicular (to the magnetic field) components of both the wave vector and Poynting vector were directed radially outward. We analyzed the event from two perspectives: excitation and propagation. The growth rate of plasmaspheric hiss remained below the threshold both inside and outside the dip, indicating that the waves were not locally excited. Regarding propagation, theoretical calculations suggest that the observed whistler-mode hiss waves were reflected by the magnetic dip in a broad frequency range. Our results indicate the important role that the magnetic structures play in the propagation of plasmaspheric hiss.
How to cite: Yue, C. and Zhuang, Y.: Abrupt Disappearance of Plasmaspheric Hiss inside the Magnetic Dip, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2062, https://doi.org/10.5194/egusphere-egu26-2062, 2026.
Chorus waves are among the most important electromagnetic whistler-mode emissions in the Earth’s inner magnetosphere and are responsible for both the energization and loss of energetic electrons in the Van Allen radiation belts. The generation of chorus is inherently related to nonlinear wave-particle interactions around the min-B equator, which result in the formation of chorus fine structure composed of individual elements sweeping in frequency. However, the details of the formation mechanism and the explanation for the spectral gap typically observed at half of the electron cyclotron frequency are still missing. One of the open questions concerns the symmetry of the generated emissions with respect to the min-B equator. We address this issue using multipoint, high-resolution measurements performed by the Cluster spacecraft. These measurements allow us to analyze a unique event in which the Cluster spacecraft move along nearly the same magnetic field line, with one spacecraft located northward and the other southward of the equator. Wave analysis based on available multicomponent measurements reveals that the waves propagate away from the equator, consistent with an equatorial source location. The structure of the upper-band chorus north and south of the equator is found to be rather different. However, the lower-band chorus emissions detected by both spacecraft are very similar, indicating that the source radiates nearly symmetrically towards both the north and south.
How to cite: Nemec, F., Santolik, O., and Pickett, J. S.: On the north-south symmetry of the equatorial whistler-mode chorus source region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5703, 2026.
Whistler instability plays a crucial role in generating whistler mode waves, which serve as the primary driver for accelerating and scattering energetic electrons in the radiation belt. Whistler instabilities are excited by the electron temperature anisotropy, where electron population exhibits a bi-Maxwellian velocity distribution. In this study, we focus on examining the growth rate and the corresponding real frequency of the whistler instability. By solving the linear kinetic dispersion equation, we investigate the dependence of the maximum growth rate and the peak frequency with plasma beta, temperature anisotropy, and hot electron abundance across a range of plasma conditions. Our results demonstrate that the maximum growth rate is significantly enhanced as plasma beta, temperature anisotropy and abundance of hot electrons increase. The peak frequency increases approximately linearly with hot electron abundance, while it exhibits an inverse trend with increasing plasma beta increases. We further establish an analytic scaling models for both the maximum growth rate and the peak frequency of whistler instability as functions of plasma beta, temperature anisotropy and abundance of hot electrons, respectively. The proposed scaling models exhibit good consistency with numerical solutions in most parameter regimes, especially when plasma beta > 0.2 and hot electrons abundance > 0.05. Our analytic models can be easily used to help characterize the physical consequences of whistler instabilities in the large-scale modeling of Earth's magnetosphere.
How to cite: Zhu, Q., Ma, X., Lou, Y., Ni, B., Li, J., and Chen, S.: Scalings for the whistler instability growth rate and corresponding real frequency for bi-Maxwellian particle distribution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5741, 2026.
In this work, we utilized a dataset of 60 relativistic electron enhancement events measured at geostationary orbit (GEO) to compare against in situ
measurements from the Van Allen Probes mission and study the radial response of outer belt fluxes and the correlation between the fluxes at GEO
and those at lower L-shells closer to the Earth. The enhancement events occurred between 1 October 2012 and 31 December 2017 and were identified
using Geostationary Operational Environmental Satellite (GOES) 15 > 2 MeV. We compare the events with fluxes measured by the Van Allen probes Energetic Particle, Composition and Thermal Plasma Suite Relativistic Electron-Proton Telescope (ECT-REPT) between 2.5 < L < 6.0 at the entire range of
energies between E = 1.8 MeV through E = 7.6 MeV. We found that the response of the radiation belts during enhancement events is very homogeneous for L > 4.0 and extremely similar for L > 5.0 at all studied energies. Post-enhancement maximum fluxes show a remarkable correlation for all L > 4.0 for all energy channels, with a maximum correlation at 4.2 MeV. We further studied the characteristic solar wind forcing leading to those relativistic electron enhancement events and characterized the L-dependent response according to the geomagnetic driver of the event.
How to cite: Pinto, V., Espitía, Y., Zenteno-Quinteros, B., Stepanova, M., and Moya, P.: Radial Evolution of Multi-MeV Relativistic Electrons during Enhancement Events at Geostationary Orbit, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21917, 2026.
Information on plasma pressure in the outer part of the inner magnetosphere is important for simulating the ring current and improving our understanding of its dynamics. Using 17 years of Cluster mission observations, we developed machine learning models to predict proton plasma pressure at energies ranging from ~40 eV to 4 MeV for stably trapped particles at L* = 5–9. The L*, location in the magnetosphere, as well as parameters of solar and geomagnetic activity, were used as predictors. The results demonstrate that the Extra-Trees Regressor model performs best. The Spearman correlation between the observations and the model's predictions is ~70%. The most important parameter for predicting proton pressure is the L* value. The most important predictor related to solar and geomagnetic activity is the F10.7 index. We demonstrate how the model performs during geomagnetically quiet periods and during moderate magnetic storms. Our results have practical applications, such as providing inputs for ring current simulations or reconstructing the three-dimensional inner magnetospheric electric current system based on magnetostatic equilibrium.
How to cite: Kronberg, E., Li, S., Mouikis, C., Luo, H., Ge, Y., and Du, A.: Predicting proton pressure in the outer part of the inner magnetosphere using machine learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11643, 2026.
A comprehensive understanding of particle acceleration and transport throughout the terrestrial magnetosphere hinges on accurate characterization of the governing electromagnetic fields. While the configuration of the magnetic field controls particle drift motions, the electric field determines the large-scale transport, energization, and particle access to different magnetospheric regions.
Although a wide range of magnetic field models exists, from idealized analytical descriptions to empirical reconstructions and self-consistent numerical simulations, representations of the magnetospheric electric field remain comparatively underdeveloped. Most commonly used electric field models are empirical and assume quasi-static conditions, often derived by mapping the solar wind dawn–dusk electric field into the polar ionosphere. Such formulations, however, omit the inductive electric field produced by the omnipresent temporal variations in the magnetic field. These inductive fields are inherently dynamic and pervasive throughout the magnetosphere, and their omission from regional and global magnetospheric models limits the model performance and misrepresents the modeled particle dynamics.
In this study, we assess the influence of inductive electric fields on particle acceleration and transport using test-particle simulations within a global MHD framework that enables decomposition of the electric field into distinct source contributions (potential and inductive sources). Simulations excluding the inductive component exhibit enhanced inward penetration of energetic particles, deformation of the Alfvén layer, and efficient particle loss along open drift trajectories toward the dayside. Conversely, inclusion of both inductive and electrostatic electric fields results in stronger particle confinement and a more stable ring current. Together, these results underscore the essential role of inductive electric fields in shaping inner magnetospheric dynamics and sustaining energetic particle populations in the region.
How to cite: Ilie, R., Liu, J., and Chen, L.: The role of inductive electric fields in shaping and stabilizing the ring current , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22060, 2026.
Three dimensional radiation belt models like the BAS radiation belt model and the VERB code assume that trapped electrons within the model space remain at a fixed kinetic energy in the absence of wave-particle interactions. However, it is also accepted that at lower energies convection due to the electric field can significantly alter the trajectories and kinetic energy of trapped electrons. Using coordinates of electric potential, magnetic field strength, and the modified second invariant (UBK), we present a mathematically simple approach to describing the full phase space of possible particle trajectories within given magnetic and electric field models. We further demonstrate that it can be used to determine the change in kinetic energy around any particle orbit, and that changing trajectories and kinetic energies can have a significant effect on satellite measurements of energy spectra.
How to cite: Daggitt, T., Glauert, S., Hendry, A., Freeman, M., and Chisham, G.: Kinetic energy variations within drift orbits: a study in UBK space, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13330, 2026.
How to cite: Katrougkalou, M. C., Kullen, A., Cai, L., Roth, L., and Zhang, Y.: NBZ currents and their connection to polar cap aurora, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20472, 2026.
Ultra-relativistic electrons in Earth’s radiation belts are strongly influenced by interactions with plasma waves and the surrounding cold plasma. Their enhancement poses a serious space-weather hazard, they can penetrate satellite shielding and damage onboard electronics.
The Van Allen Probes mission was able to observe most energetic electrons exceeding 7 MeV in the Earth’s outer radiation belt. The acceleration of these particles under cold-plasma density variations has been successfully simulated for single events, but comprehensive statistical validation has not yet been performed. This study evaluates, in a statistical framework, how cold plasma density influences density-dependent wave particle interactions and the dynamics of 7.7 MeV radiation-belt electrons. We conducted three groups of density-driven VERB (Versatile near‐Earth environment of Radiation Belts and ring current) simulations in which cold plasma density was used to scale the wave-particle diffusion coefficients: one using static density from an empirical model, one using Van Allen Probes in-situ plasma density observations, and one using plasmaspheric densities predicted by the physics-based VERB-Convection Simplified (VERB-CS) model.
The study highlights the importance of coupling radiation belt models with more realistic plasmaspheric models and the need to improve plasmaspheric representations to better understand electron acceleration.
How to cite: Santhini, P., Shprits, Y., Haas, B., Wang, D., Lyu, X., and Fu, H.: Role of Plasmaspheric Density in Reproducing Observed Ultra-Relativistic Electron Enhancements: A Statistical Analysis Using VERB Simulations , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6741, 2026.
Lightning whistlers play an important role in the loss of energetic electrons from the Van Allen radiation belts and their overall dynamics. Whistlers are generated by atmospheric lightning strokes and due to a few thousands of thunderstorms occurring simultaneously at any moment, they are very common in the satellite measurements. However, manual whistler identification is very time consuming and unfeasible on a large scale. In this work, we introduce an automatic whistler identification and analysis routine that identify individual whistlers and determine their dispersion from DEMETER satellite burst mode measurements. For this purpose, we use machine learning approach. Specifically, YOLOv11 and Faster R-CNN object detection techniques for whistler identification and genetic algorithm for analysis of their dispersion. We use a manually identified dataset of about 600 spectrogram images containing approximately 6,000 whistlers to train both models. Overall, we detect several millions of whistlers in DEMETER burst mode measurements. Comparing both models with whistler detection neural network onboard DEMETER we observe similar behavior between all three models. During the northern summer rich on thunderstorms, low-dispersion whistlers are observed more frequently in the Northern Hemisphere and high-dispersion whistlers are observed more frequently in the Southern Hemisphere. The results demonstrate that modern object detection techniques can be an eligible and robust approach for plasma wave identification and provide a valuable basis for future plasma wave studies.
How to cite: Linzmayer, V., Nemec, F., Santolik, O., and Kolmasova, I.: Lightning whistlers in DEMETER Satellite Data: Identification and Properties, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5724, 2026.
Power line harmonic radiation (PLHR) is an important anthropogenic source of electromagnetic waves generated by power networks. It appears at harmonic frequencies of the fundamental power grid frequency, and these harmonics can reach up to several thousand Hz. In this study, we analyse PLHR using wave measurements from the ground-based PWING network. This study primarily focuses on measurements conducted in northern Finland, specifically at Angeli (69.02°N, 25.82°E), Kannuslehto (67.74°N, 26.27°E), and Oulujarvi (64.51°N, 27.23°E). Wave intensity data with a high frequency resolution (1 Hz) are used to investigate the properties of PLHR from 50 Hz up to 1000 Hz, particularly its dependence on geomagnetically induced currents (GICs) associated with space weather events. The wave data are complemented by nearby 1 s magnetometer measurements from the Finnish IMAGE network stations, which are used to estimate GIC strength via the temporal variation of the horizontal magnetic field component (dB/dt). Preliminary results for geomagnetic storms of October 2024 and January 2025 indicate that the intensity of PLHR is significantly enhanced by an order of magnitude during geomagnetic active times, particularly for even harmonics at 300 Hz, 600 Hz, and 900 Hz, which are usually weak or absent in well-operating power systems and appear mostly when the current waveform gets distorted. We also investigate a possible delay between GIC events and the resulting distortion of the current waveforms, and discuss the implications for the required time resolution of magnetometer data.
How to cite: Drastichova, K., Nemec, F., Shiokawa, K., Martinez-Calderon, C., Manninen, J., and Raita, T.: Ground-Based PWING Observations of Power Line Harmonic Radiation in Finland During Geomagnetic Disturbances: Initial Results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5749, 2026.
How to cite: Li, J., Lou, Y., Gu, X., Ni, B., Zhu, Q., Ma, X., and Chen, S.: Spatial Distribution and Geomagnetic Dependence of Radiation Belt Electron Reversed Energy Spectrum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6164, 2026.
How to cite: Ma, X., Chen, S., Ni, B., Lou, Y., Xiang, Z., and Zhu, Q.: Dependence of Low-Frequency Plasmaspheric Hiss on Geomagnetic Activity and Solar Wind Dynamic Pressure and Its Electron Scattering Effects, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8533, 2026.
Field line resonance (FLR) is an important source of Ultra-low-frequency (ULF) waves observed in the inner magnetosphere. In this study, we present multi-spacecraft observations of a toroidal ULF wave, detected by the Arase, Van Allen Probe-A (VAP-A), and GOES-14. During the event, Arase and VAP-A were positioned on two magnetic field lines in close proximity, providing a rare opportunity to examine the latitudinal structure of FLR. The temporal profiles of these toroidal components exhibited distinct, separated wave packets, with each packet persisting for ~10 minutes and one-to-one correspondence in timing and amplitude across all three spacecraft. The observed waveforms resemble transient toroidal waves associated with impulsive disturbances in the near-Earth magnetotail. These toroidal waves are identified as fundamental waves based on phase differences and harmonic eigenfrequencies. The oscillations observed in the residual flux of protons, along with the bump-on-tail structure, suggest that the waves are likely generated by drift resonance.
How to cite: Wang, Z., Liu, W., and Zhang, D.: Multi-spacecraft observations of a fundamental toroidal ULF wave event, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6326, 2026.
The acceleration mechanisms of relativistic electrons in the outer radiation belt have been widely investigated during geomagnetic storms. However, non-storm time acceleration of relativistic electrons attracts less attention and its underlying mechanism has yet well understood. Here we investigate a rapid acceleration event for > ~MeV relativistic electron at L* > 5 after moderate substorm during the non-storm period of 13-15 January, 2013. To clarify the roles of potential physical mechanisms, a 3D numerical simulation including two typical radial diffusion models and event-specific chorus waves is conducted. The simulation results are further compared with Van Allen Prboe observations. The comparison shows that the dominant mechanism for the relativistic electron acceleration during this non-storm event exhibit clear energy-dependence. Specifically, radial diffusion plays a dominant role in ~MeV electron acceleration whereas local diffusion driven by chorus waves primarily accelerate ~2 MeV electrons. In addition, the combination of both mechanisms facilitates the acceleration process more effectively than either alone and can well capture the enhanced magnitude of electron phase space densities, thus underscoring a robust cooperative role in relativistic electron acceleration. Our results suggest the competition and incorporation of radial diffusion and local acceleration driven by chorus in relativistic electron acceleration. Our study advances the understanding of relativistic electron acceleration mechanisms during non-storm periods, providing insights for optimizing radiation belt modeling and prediction.
How to cite: Wang, X., Cao, X., Ni, B., Wang, D., and Lu, J.: Roles of Radial Diffusion and Chorus-driven Diffusion in the Outer Belt Relativistic Electron Acceleration During the Non-Storm Period of 13–15 January 2013, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11378, 2026.
Plasmaspheric hiss is a whistler-mode emission in the Earth’s plasmasphere and is a major contributor to the pitch-angle scattering and loss of radiation belt electrons. Previous statistical studies based on single-satellite observations have limited a systematic understanding of plasmaspheric hiss waves. In this study, we present a statistical analysis of plasmaspheric hiss using combined observations from the Van Allen Probes and the Arase spacecraft during 2012-2024. The use of two missions improves spatial coverage and enables a more comprehensive characterization of the hiss intensity distribution within magnetic latitudes up to 45°. The results show that hiss intensity is enhanced on the dayside and peaks at L ≈ 3-4. Based on these results, we develop an empirical regression model that parameterizes the dependence of the root-mean-square hiss magnetic field intensity on L-shell, magnetic local time (MLT) and magnetic latitude (MLAT). The influence of geomagnetic activity is further parameterized using polynomial fits to the Kp index. The model is applicable for L ≤ 6.5, Kp ≤ 6, all MLTs, and MLAT up to 45°, providing a practical representation of plasmaspheric hiss for radiation belt modeling applications.
How to cite: Liu, Y., Wang, D., Fu, H., Shprits, Y. Y., Miyoshi, Y., Kasahara, Y., Kumamoto, A., Matsuda, S., Matsuoka, A., Hori, T., Shinohara, I., Tsuchiya, F., Teramoto, M., Yamamoto, K., and Shinbori, A.: A Multi-Satellite Statistical Analysis and Empirical Model of Plasmaspheric Hiss Based on Van Allen Probes and Arase Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12762, 2026.
Chorus waves play a significant role in the dynamic evolution of energetic electrons in the inner magnetosphere. Therefore, understanding the spatial and temporal dynamics of these electrons requires global distributions of chorus waves, which in turn necessitates combining data products from multiple satellite missions to achieve sufficient spatial coverage. In this study, we use 11 years of data from both the Van Allen Probes and the Arase satellite to create a global model of the magnetic intensity of chorus waves. The agreement between the two satellite missions was assessed using observations during close conjunctions. The statistical model is based on data with good spatial coverage up to 40° magnetic latitude, across all magnetic local times (MLT), and at high L-shells, resulting in a model with excellent spatial continuity. The model is generated for both Upper-Band Chorus (UBC; 0.5 fce < f < fce) and Lower-Band Chorus (LBC; 0.05 fce< f < 0.5 fce) waves, where fce is the equatorial electron gyrofrequency. These models are parameterized by the Kp index of geomagnetic activity and expressed as functions of L-shell, magnetic latitude (λ), and MLT. Our model is well suited for inclusion in quasi-linear diffusion calculations of electron scattering rates and particle simulations in the inner magnetosphere.
How to cite: Roy, A., Wang, D., Miyoshi, Y., Shprits, Y., Hanzelka, M., Feng, H., Lyu, X., Santolík, O., Feng, T., Lepage, T., Reeves, G., Kasahara, Y., Matsuda, S., Shinbori, A., Tsuchiya, F., Kumamoto, A., Matsuoka, A., Teramoto, M., Yamamoto, K., and Shinohara, I.: Developing Analytical Chorus Wave Models Using the Data from Van Allen Probes and Arase Satellite, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12869, 2026.
Quasi-trapped electrons (pitch angle in DLC) in Earth's inner radiation belt are an important particle population whose behaviors help reveal the scattering effects of trapped electrons and quantify the intensity of electron precipitation. However, a detailed systematic characterization of quasi-trapped electron energy spectra in inner belt has not yet been investigated. Here we present a statistical study of quasi-trapped electron energy spectra based on 8-year DEMETER measurements. The electron energy spectral are classified into three categories: CRAND-produced, ROH (Raise-On-Head), and exponential-type. More than 95% of the energy spectra can be categorized as one of these three energy spectrum types, while 10.12% are CRAND energy spectra, 75.78% are ROH energy spectra, and 9.19% are exponential energy spectra. Through event analysis and statistical analysis of distributions of spectral types and characteristic parameters, we analyze the spatiotemporal evolution of quasi-trapped electrons in the inner radiation belt and investigate the source mechanisms of quasi-trapped electrons. The CRAND energy spectrum is predominantly distributed at L<=1.2, which is very stable and remains unchanged during active geomagnetic activities. The ROH energy spectrum is the most dominant type of quasi-trapped electron in the inner radiation belt. The exponential energy spectrum occurs at L~3 during intense magnetic storms, with a tendency moving to lower L. Notably, exponential energy spectra are also observable at L ~ 2.5 with the longitude =240°-300° during geomagnetically quiet periods, which may be due to electron drift accumulation. These results provide new insights of inner belt electron dynamics.
How to cite: wang, J., xiang, Z., ni, B., liu, Y., dong, J., hu, J., and guo, H.: A Statistical Study of Quasi-trapped Electron Energy Spectrum: DEMETER Measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16250, 2026.
Much is still unknown about the auroral region. STEVE (Strong Thermal Emissions Velocity Enhancement), a mauve-white sub-auroral emission that gained scientific recognition in 2015, is one such case. High electron temperatures (over 6000 K) and fast ion drift speeds (over 10 km/s) have been reported within STEVE by the European Space Agency's Swarm satellites. If true, STEVE is embedded in an extreme plasma environment compared with typical high-latitude ionospheric conditions. The goal of this study is to investigate the extent that these reported environments can be corroborated. We report 28 new STEVE event conjunctions between Swarm satellites and ground-based observations previously not reported in the literature. One STEVE event found demonstrated ion drift speeds above 15 km/s, well outside of the instrument's functional range. By using the new reported STEVE values, thermal ion imaging (TII) Monte Carlo simulations for Swarm's electric field instrument detectors are used to substantiate or refute the most extreme STEVE events. These results are compared to the new Swarm TRACIS (TII Raw And Corrected Imagery/Spectra) dataset, demonstrating raw particle energy data to validate these reported ionospheric conditions. This project's results provide greater insight into STEVE as an extreme ionospheric plasma environment and inform future satellite measurement techniques aiming to study aurora.
How to cite: Borges, V.: STEVE as an Extreme Ionospheric Plasma Environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13894, 2026.
The long observational record of POES satellites (1979 to present) is often used to estimate the EEP and study its long-term evolution and atmospheric impacts. The unique POES record has been the basis for the CMIP6 and CMIP7 versions of the EEP forcing recommended as an input to chemistry-climate models. While the POES measurements provide a long and nearly continuous data series they suffer, among other things, from poor energy resolution. They measure the energetic electrons with 3 integral channels spanning from >30 keV, >100 keV to >300 keV.
There are strong indications that the relativistic part of the EEP spectrum, largely missed by the POES observations, is likely to be important because of the direct ionization it produces in the mesosphere. Typically, the high-energy part of the EEP spectrum is estimated by a power-law extrapolation from lower energies, but this might not be accurate.
Here we present preliminary results combining the recently homogenized record of POES observations to another record of energetic electron measurements made at low-Earth orbit by the Proba-V satellite during 2013-present. Together these measurements cover energies from 30 keV to 8 MeV. We describe here the construction of the dataset and the methods used to join the Proba-V measured spectra to the spectra measured by POES, and finally evaluate the resulting atmospheric ionization.
How to cite: Mantere, J., Asikainen, T., and Salminen, A.: A new composite of energetic electron precipitation and resulting atmospheric ionization based on combined POES and Proba-V data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17639, 2026.
We present a new method with a Graphical User Interface (GUI), allowing to inspect 15 years of Cluster mission (2002-2017) to derive plasmapause positions (PP).
The PP are deduced from electron density data derived from WHISPER relaxation sounder wave measurements, which is limited up to around 150 cm-3.
It is important to note that our approach allows us to identify the PP during geomagnetically quiet periods, which is a challenging issue as during such periods plasmapause becomes diffused and its boundary can be hard to determine.
After reviewing and validating the PP, we obtained a dataset containing more than 4000 PP positions.
It is our objective that this dataset will eventually become available as a high-level data product in the Cluster Science Archive (CSA).
The obtained PP dataset can be very valuable for future studies of plasmapause formation and evolution, as well as interaction with the radiation belts. This can contribute to improving understanding of space weather's impact on the Earth's magnetosphere.
How to cite: Bandić, M., Verbanac, G., Živković, S., Ivanković, L., Masson, A., and Dandouras, I.: The new plasmapause dataset based on Cluster , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19180, 2026.
NASA Reuven Ramaty High Energy Solar Spectroscopic Imager RHESSI and ESA PROBA-1 satellites, both flying the Low Earth Orbit, and equipped with small radiation monitors were used in this study. Proba-1 was launched on Oct 22nd, 2001 in the sun-synchronous orbit and is still in operation. It is a small autonomous satellite developed for Technology Demonstration Program of ESA. Its primary goal was to test satellite autonomy. Its secondary objective was space environment investigation with Standard Radiation Environment Monitor SREM. Its three Si-diode detectors are optimized to measure electrons and protons encountered in the Earth Radiation Belts. Level 2 SREM data provide time resolved particle spectra along Proba-1 orbit. RHESSI was launched into space on February 5th, 2002 as NASA Small Explorer and operated until August 2018. Its Ge-spectrometer provided first ever permanent images of the Sun at wide range of X-ray energies. RHESSI small radiation monitor measured electrons with energies from about 65 keV and protons from above 28 MeV using well shielded Si-diode. The monitor, looking perpendicularly from the spacecraft rotation axis, allowed for sampling angular distribution of incoming particles. Inside the South Atlantic Anomaly SAA, the pointing direction of RHESSI nearly aligns with the geomagnetic field vector. This way angular distributions over the full range of pitch angles along the magnetic field line were measured. We discuss evolution of electron and proton pitch angles inside the SAA during the second half of solar cycle 23 and almost the whole solar cycle 24. Specific examples of observed features including anisotropies related to particle loss are provided. Impact of directionality distribution on radiation models is given, based on cross-comparison with Proba-1 observations.
How to cite: Hajdas, W. and Zhang, P.: Mapping pitch angle distribution of electrons and protons in the South Atlantic Anomaly between 2002 and 2018, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16138, 2026.
Quasi‐periodic (QP) emissions, a type of whistler‐mode electromagnetic waves with QP intensity modulation, play a significant role in magnetospheric electron dynamics through wave‐particle interactions. While previous studies have identified QP events via manual spectrogram inspection, here we present an automated detection method leveraging coherence analysis of simultaneous measurements from the China Seismo‐Electromagnetic Satellite and Van Allen Probes to systematically characterize coherent QP emissions. From October 2017 to July 2019, 224 coherent QP events were identified across conjugate satellite combinations. These events exhibit frequencies spanning from ∼500 to 2,600 Hz, with majority concentrated between 600 and 2,200 Hz, and modulation periods ranging from 10 to 220 s (median: 47 s). Equatorial distribution reveals a duskside (12–18 magnetic local times (MLT)) dominance in occurrence rates, consistent with plasmaspheric density asymmetries. The spatial extents of the majority QP emissions are predominantly ∼3.5 RE in radial direction and ∼2 MLT in azimuthal direction. Events with shorter modulation periods (≤47 s) extend more broadly, reaching maximum observed extents of 6 RE radially and 6 MLT azimuthally. Our results are of interest for studying the origin and propagation of the QP emission.
How to cite: He, B.: Statistical Study on Coherent Quasi‐Periodic Emissions Based on Multi‐Satellite Measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4374, 2026.
Ultra-low frequency (ULF) waves play a critical role in energy transport within the magnetosphere-ionosphere (M-I) coupling system. Using approximately 7-years of Arase satellite observations, we perform a comprehensive statistical analysis of the field aligned Poynting flux (S//) in the Pc5 band in the inner magnetosphere. A pronounced enhancement in S// at higher latitudes is consistent with the trend inferred from the product of electric and magnetic wave amplitudes modeled by Cummings et al. (1969). Comparison between inward and outward fluxes reveals a net energy flux toward the ionosphere, indicating energy dissipation in the ionosphere. To understand the cause of this net energy flux, a simplified model illustrates how the phase difference between electric and magnetic fields (θEB) affect net S//, suggesting that phase shifts, likely induced by ionospheric dissipation, play a key role in modulating S//. Latitudinal profiles of S// and θEB for poloidal and toroidal modes at 6.82 mHz within L = 5.5 - 6.5 further demonstrate this effect of θEB on S//. The magnetic local time (MLT) dependence of S// shows pronounced day-night asymmetry at higher latitudes, with stronger fluxes on the nightside, consistent with variations in ionospheric conductance. Finally, the latitudinal distribution of S// under varying geomagnetic activity conditions exhibits systematic enhancements with increasing Kp, particularly at higher latitudes. These results provide offer insights into the dynamics of energy dissipation and transport within the M-I coupling system.
How to cite: Yan, L., Liu, W., Zhang, D., Wang, Z., Zhou, X.-Z., Sarris, T., Li, X., Tong, X., Matsuoka, A., Kasaba, Y., Kasahara, Y., Miyoshi, Y., Hori, T., Yamamoto, K., Shinohara, I., and Teramoto, M.: Characteristics of Field Aligned Poynting Flux of Pc5 ULF Wave Based on Arase Measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4885, 2026.
The electron density of the D-region ionosphere (60–100 km) plays a critical role in radio communications, navigation systems, and space environment monitoring. Despite its importance, this region remains difficult to observe. Traditional ground-based Very Low Frequency (VLF) monitoring typically relies on single propagation path measurements, yielding only path-averaged information. In this study, we image the D-region ionosphere using VLF network observations and a particle filter.
To address the non-linear and ill-posed problems inherent in D-region ionosphere inversion, we applied a particle filter algorithm to the reconstruction process. The numerical experiments demonstrate the efficacy of the particle filtering approach in D-region ionosphere imaging. Furthermore, we used this method to image the evolution of the D-region ionosphere during a solar eclipse and a solar flare. The results demonstrate the significant promise of the method for remote sensing the D-region ionosphere using VLF network observations, offering a new capability for monitoring the impacts of space weather events on the lower ionosphere.
How to cite: Ma, W., Xu, W., Gu, X., Wang, S., Ni, B., Cheng, W., Feng, J., Xu, H., Pan, Y., and Shi, H.: Imaging the D-Region Ionosphere Using VLF Network Observations and a Particle Filter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22589, 2026.
Electrons of several hundred keV in Saturn’s ring current are important seed components of the radiation belt. In this study, we statistically analyzed the spatial distribution of energetic electrons in the equatorial inner magnetosphere using Cassini in-situ observations. We found that, across all energy channels, the peak position of the energetic electron flux shifts from the midnight sector to the afternoon sector as the L shell increases. At specific L shells, the transitional energy (), which separates the peaks of energetic electron flux in azimuthal direction, decreases as L shell increases and is consistent with the theoretical prediction of corotation drift resonant energy (). Further analysis indicates that the day-night asymmetry of energetic electron flux is caused by the noon-to-midnight electric field, with its direction deviating from the noon-midnight line. These findings advance our understanding of the energization mechanism of inward radial transport.
How to cite: Yue, C. and Li, Y.: Local Time Asymmetry in Energetic Electron Distribution within Saturn's Inner Magnetosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2079, https://doi.org/10.5194/egusphere-egu26-2079, 2026.
Saturn’s ring current, which regulates the global field configuration, exhibits dynamic variations due to the hot plasma injections. However, it’s difficult to quantify the transient magnetic field disturbance without local measurements on the surface of Saturn. Using a forward simulation method, we extracted the energetic ion distributions from energetic neutral atom (ENA) images, thereby estimating the energy content from the suprathermal ring current particles and corresponding magnetic field disturbance. We analyzed the ring current energy content and magnetic field perturbations during a dynamic event and show that suprathermal ring current energy tripled after injection, then rapidly decayed in the subsequent planetary rotation period. The magnetic field depression at the equator of planetary surface is ~21 nT after the injection, which is equivalent to a small geomagnetic storm in Earth's magnetosphere. The internal plasma sources and neutral gas environment result in the differences in ring current dynamics of Saturn and Earth, revealing the signatures of giant planet magnetosphere.
How to cite: Li, Y. and Yue, C.: Magnetic Field Disturbance Induced by the Enhanced Suprathermal Ring Current in the Magnetosphere of Saturn, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6421, 2026.
Energetic electrons in Earth's inner radiation belt pose significant hazards to spacecraft systems, with the strongest radiation in low-Earth orbit (LEO) mostly confined to the South Atlantic Anomaly (SAA) region. Once considered stable, the inner belt is now understood to exhibit significant variability. Using data from the low-Earth-orbit Macau Science Satellite-1 mission, we report transient distortions of the SAA radiation environments, observationally characterized by enhanced fluxes of energetic electrons either attached to or detached from the traditional SAA boundary. We show that these distortions are induced by large-scale electric-field perturbations that adiabatically alter the electron mirror heights, which can be further modulated by ultra-low-frequency waves. Test-particle simulations successfully reproduce the observational features and provide new constraints on the properties of the associated electric fields. These findings reveal a less recognized variability of the inner belt, extending the electron radiation risks beyond the expected SAA boundaries.
How to cite: Zhou, X., Yin, Z.-F., Sun, Y.-X., Zong, Q.-G., Liu, Y., Hu, Z.-J., Omura, Y., Rankin, R., and Zou, H.: Transient Distortions of the South Atlantic Anomaly Radiation Environments Driven by Large-Scale Electric Fields, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22004, 2026.
