In the polar middle and upper atmosphere, Nitric Oxide (NO) is produced in large amounts by both solar EUV and X-ray radiation and energetic particle precipitation, and its chemical loss is driven by photodissociation. As a result, polar atmospheric NO has a clear seasonal variability and a solar cycle dependency which have been measured by satellite-based instruments. On shorter timescales, NO response to magnetospheric electron precipitation has been shown to take place on a day-to-day basis. Despite recent studies using observations and simulations, it remains challenging to understand NO daily distribution in the mesosphere-lower thermosphere during geomagnetic storms, and to separate contributions of electron forcing and atmospheric chemistry and dynamics. This is due to the uncertainties existing in the available electron flux observations, differences in representation of NO chemistry in models, and differences between NO observations from satellite instruments. In this paper, we use mesospheric-lower thermospheric NO column density data measured with a millimeter-wave spectroscopic radiometer at the Syowa station in Antarctica. In the period 2012 - 2017, we study both the long-term and short-term variability of NO. Comparisons are made with results from the Whole Atmosphere Community Climate Model (WACCM) to understand the shortcomings of current electron forcing in models and how the representation of the NO variability can be improved in simulations. We find that, qualitatively, the simulated year-to-year variability of NO is in agreement with the observations. On the other hand, there is up to a factor of two underestimation of the NO column density in wintertime, and the model captures only 27% of the measured magnitude in the day-to-day variability. The observed day-to-day variability has a good correlation with three different geomagnetic indices, indicating the importance of electron forcing in atmospheric NO production. Using electron flux measurements from the Arase satellite, we demonstrate that mesospheric electron forcing has potential to significantly increase the NO column density.
How to cite: Verronen, P., Mizuno, A., and Miyoshi, Y. and the Research Team: Electron-Driven Variability of the Upper Atmospheric Nitric Oxide Column Density Over the Syowa Station in Antarctica, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5637, https://doi.org/10.5194/egusphere-egu25-5637, 2025.
Ionospheric disturbances play a critical role in radio wave propagation, with implications for communication, navigation systems, and understanding space weather dynamics. Among the tools used to probe these disturbances, relative ionospheric opacity meters (riometers) provide valuable insights by measuring cosmic noise absorption (CNA). These absorption events offer a window into the diverse physical processes driving energetic electron precipitation and their subsequent impact on the ionosphere.
This study utilizes observational data from the University of Calgary network of single-frequency wide-beam (GO-Canada) riometers. A classification system was developed to segregate riometer absorption events into distinct groups based on their time-lagged signatures observed across different longitudes by stations in the East-West chain of the riometer network.
We investigate the correlation between wave occurrences measured onboard the THEMIS satellite and electron precipitation inferred from riometer absorption measurements across various event types. The goal is to determine whether these correlations align with established geophysical processes, such as precipitation driven by whistler-mode waves, and to quantify the strength and significance of these relationships. By examining the temporal and spatial patterns of cosmic noise absorption events in conjunction with satellite-based measurements, we aim to provide a detailed assessment of how well these phenomena correlate. This analysis seeks not only to validate the underlying geophysical mechanisms but also to enhance our quantitative understanding of the role of whistler-mode waves in driving electron precipitation and subsequent ionospheric disturbances.
How to cite: Ghaffari, R., Cully, C., Spanswick, E., Fiori, R., and Gillies, R.: Exploring the Link Between Cosmic Noise Absorption Events and Whistler-Mode Waves, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11520, https://doi.org/10.5194/egusphere-egu25-11520, 2025.
The energetic particle precipitations (EPPs), which include solar proton events (SPEs) and energetic electron precipitations (EEPs), can significantly impact ozone levels in the polar middle atmosphere through two main mechanisms. One is the direct impact that the energetic protons can attend the mesosphere and catalyze ozone depletion through the ionized odd hydrogen. Another is the indirect impact that the downward branch of the residual circulation transports the ionized odd nitrogen to the stratosphere and causes a long‐term effect on ozone. In this study, we conduct case studies and statistical analyses of ozone observations from the Aura satellite to investigate these two mechanisms. For the direct impact, we find that the mesospheric ozone depletion during SPEs is more pronounced at higher geomagnetic latitudes and negatively correlates with the proton flux, while during EEPs the ozone depletion predominantly occurs in the geomagnetic latitude band of 60–70°. For the indirect impact, our results show no significant correlation between proton flux and stratospheric ozone depletion. However, when analyzing the vertical velocity of the residual circulation from the stratospheric ozone depletion trajectory, we find a notable SPE effect during winter. The SPEs modulate both horizontal and vertical circulation, which further influences ozone levels. This study further validates the physical link between the magnetosphere and atmosphere and promotes our understanding of the solar influence on Earth's climate.
How to cite: Wang, Y., Li, H., Li, Y., Pan, Y., Xu, W., and Wang, C.: Effects of Energetic Particle Precipitations on Polar Middle Atmosphere Ozone: Direct and Indirect Mechanisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7681, https://doi.org/10.5194/egusphere-egu25-7681, 2025.
Energetic electron precipitations (EEPs) from the inner magnetosphere are mainly caused by waves, for example, whistler mode chorus waves, hiss waves, electromagnetic ion cyclotron waves, and electrostatic cyclotron harmonic waves. EEPs can influence the atmosphere by triggering auroral emissions and producing NOx in the upper atmosphere. Therefore, it is very important to quantify the EEPs by waves and their effects on the atmosphere.
In this presentation, we will present new lifetime models of energetic electrons that we developed recently to quantify the EEPs caused by whistler mode chorus waves. Using these lifetime models, we perform numerical simulations to calculate the precipitation of energetic electrons from the inner magnetosphere. Using the calculated EEPs, we calculate ionization rates, which quantify how efficiently precipitating particles interact with atmospheric molecules. We show that the inclusion of additional scattering mechanisms, beyond those accounted for in up-to-date hiss and chorus models, is essential for the accurate estimation of precipitated electrons and their atmospheric effects.
How to cite: Wang, D., Shprits, Y., Haas, B., Drozdov, A., Grishina, A., Sinnhuber, M., and Haenel, F.: Quantifying Energetic Electron Precipitation by Wave-Particle Interactions in the Inner Magnetosphere and Their Atmospheric Impacts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17934, https://doi.org/10.5194/egusphere-egu25-17934, 2025.
Energetic Electron Precipitation (EEP) has been shown to influence wintertime stratospheric dynamics through the production of NOy species, which subsequently deplete ozone in the wintertime lower mesosphere and upper stratosphere. It has been shown previously that EEP can influence the occurrence probability of sudden stratospheric warmings (SSWs) where the wintertime stratospheric polar vortex breaks. Here we show that EEP also influences the evolution of the stratospheric polar vortex during and after the SSWs.
These results indicate that incorporating EEP into climate forecast models can potentially enhance the predictability of wintertime stratospheric dynamics and their influence on surface weather patterns. These results highlight the role of EEP in refining seasonal stratospheric and surface weather predictions.
How to cite: Vokhmianin, M., Asikainen, T., and Salminen, A.: Role of Energetic Electron Precipitation in Shaping Stratospheric Vortex Evolution Following Sudden Stratospheric Warmings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19954, https://doi.org/10.5194/egusphere-egu25-19954, 2025.
Precise energy spectrum information is crucial for quantifying the impact of energetic electron precipitation into the atmosphere, as the penetration depth (the altitude at which the electrons deposit their energies) is strongly energy dependent. However, acquiring continuous spectrum data over a wide energy range (30 keV to 6 MeV) using a single instrument is challenging due to electronic saturation at lower energies and low count rates at higher energies. REPTile-2 (Relativistic Electron and Proton Telescope integrated little experiment-2), an advanced version of the REPTile instrument flown on the CSSWE CubeSat (2012-2014), measured 0.25-6 MeV electrons in 60 channels onboard the CIRBE (Colorado Inner Radiation Belt Experiment) CubeSat and revealed many features and dynamic variations of the relativistic electrons, thanks to its high energy resolution (ΔE/E <10%). CIRBE was launched into a highly inclined low Earth orbit (LEO) on April 15, 2023, and re-entered on October 4, 2024. To measure the lower energy electrons, the Medium Energy Electron Telescope (MEET) has been developed at the University of Colorado Boulder/LASP, leveraging the heritage of REPTile-2. MEET measures 30–800 keV electrons (and 1.1–60 MeV protons) in 59 channels with an energy resolution (ΔE/E) of <20% for 30–76 keV, <10% for 76–140 keV, and <5% for 140–800 keV. The combined capabilities of REPTile-2 and MEET will address the challenge of measuring energetic electrons with high energy and time resolution across a broad energy range (30 keV to 6 MeV) in LEO, which will enable the quantitative assessment of their impact to various processes in the atmosphere and ionosphere.
How to cite: O'Brien, D., Li, X., and Hogan, B.: Quantifying Energetic Electron Precipitations: A Combined REPTile-2 and MEET Approach to Measure 30keV – 6MeV with High Energy Resolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2397, https://doi.org/10.5194/egusphere-egu25-2397, 2025.
Auroral particle precipitation (<30 keV) is usually assumed to be equally strong for both signs of the By component of the interplanetary magnetic field (IMF). However, recent statistical studies have showed that geomagnetic activity is significantly modulated by the signs and amplitudes of IMF By and the Earth's dipole tilt angle Ψ. Here we quantify this By dependence for auroral electron precipitation for the first time. Furthermore, we make a case study on a sequence of high-speed stream (HSS) driven events of auroral and medium energy (>30 keV) particle precipitation. We show that when HSSs are comparable in terms of IMF and solar wind parameters, HSSs with opposite signs of By and Ψ can lead to systematically stronger particle precipitation in individual events. We perform a superposed epoch analysis of 485 HSSs giving further evidence that the By-effect is especially significant during HSSs. This is likely due to the persistent IMF By polarity during HSSs.
How to cite: Laitinen, J., Holappa, L., and Vanhamäki, H.: A Combined Effect of the Earth's Magnetic Dipole Tilt and IMF By in Controlling Auroral Electron Precipitation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10521, https://doi.org/10.5194/egusphere-egu25-10521, 2025.
The Earth's magnetic field is a complex structure, exhibiting varying strengths across different coordinates. Of particular interest is the South Atlantic Anomaly (SAA), a region characterized by a weak magnetic field and intense precipitation processes. Accurate modeling of electron precipitation above this area demands a comprehensive approach, involving the calculation of magnetic fields and electron bounce. Incorporating realistic field models, such as Tsyganenko (1989; T89) for external and Internation Geomagnetic Reference Field (IGRF) for internal fields, is essential for correct modeling. Furthermore, dividing the loss cone into drift and bounce loss cones, correlated with geomagnetic longitudes, has to account for more accurate numbers of precipitated particles. By simulating a geomagnetic storm occurring in June 2016 and validating our findings against observations from the Electron Losses and Fields INvestigation instrument on board the Lomonosov satellite (ELFIN-L) in low-Earth orbit, we studied and compared precipitation activities during both quiet and disturbed geomagnetic conditions of this event. Our investigation underscores the significance of incorporating the non-dipole loss cone model and bounce-averaged lifetimes incorporated into the loss cone losses, leading to calculated drift loss cone flux, and potentially - of the precipitated flux. In our study, we show the importance of the non-dipole magnetic field models utilization leading to prospective improvement in estimation of different flux populations.
How to cite: Grishina, A., Shprits, Y., Drozdov, A., Wang, D., and Haas, B.: Modeling of the Electron Precipitated Flux in Non-dipole Magnetic Field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10056, https://doi.org/10.5194/egusphere-egu25-10056, 2025.
Widely used geomagnetic activity indices such as Kp or Dst are derived from the combined data from several geomagnetic observatories that are distributed over the globe to provide a global index. Forecasting such indices is crucial as solar-driven geomagnetic activity can significantly affect both technology and human activities on Earth and in the near-Earth space environment.
We developed a new model to forecast geomagnetic indices by incorporating predicted data from individual observatories. Unlike previous models that relied directly on an index and ignored diverse physical effects at individual observatories, this approach considers each observatory separately in the forecasting process. It thus produces predictions of global geomagnetic indices that integrate the same physical principles as in the original calculations of the Kp index.
We demonstrate the performance of the model for the Kp index along with the recently derived Hpo indices, which all measure planetary geomagnetic disturbances caused by solar activity. The Hpo indices, Hp60 and Hp30, provide high-resolution (hourly and half-hourly, respectively) representations of these disturbances, similar to the 3-hourly Kp index but without the upper limit of 9. The model demonstrates good agreement, accurately capturing trends and overall behaviour, even with sparse solar wind data.
How to cite: Kervalishvili, G., Michaelis, I., Rauberg, J., Korte, M., and Matzka, J.: A new approach for predicting geomagnetic Kp and Hpo indices using machine learning techniques, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7225, https://doi.org/10.5194/egusphere-egu25-7225, 2025.
During the Juice (Jupiter Icy Moons Explorer) flyby of Earth in August 2024, the spacecraft traversed the magnetosphere in the time span of about 12 hours. The mass spectrometer Jovian Plasma Dynamics and Composition Analyzer (JDC) has the capability to observe, within a hemisphere, electrons in the energy range of a few eV/q - 35 keV/q, and positive and negative ions with masses between 1 and 70 amu, in the energy range of a few eV/q - 35 keV/q.
The measurements of JDC enabled us to characterize the state of the Earth’s magnetosphere at this point in time. The spacecraft passed through all key plasma domains and boundaries and the data taken provide a semi-instantaneous view of the magnetosphere. The plasmasphere, the ring current, the radiation belt and the magnetosheath are probed. Multiple crossings of the magnetopause are seen as well as foreshock phenomena upstream of the bow shock. The plasma populations recorded are compared to the typical plasma parameters characterizing each region, taking upstream conditions and geomagnetic indices into account. The observations of the radiation belt are compared with a location-dependent radiation belt model. The data shows the excellent performance of the versatile mass spectrometer and clearly shows how an interplanetary mission can contribute to magnetospheric science.
How to cite: Stenberg Wieser, G., Wieser, M., Barabash, S., Wittmann, P., Karlsson, S., Krupp, N., Roussos, E., Fraenz, M., Wurz, P., and Brandt, P. and the PEP team: A snapshot of the particle environment in the Earth’s magnetosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12611, https://doi.org/10.5194/egusphere-egu25-12611, 2025.
The interaction between the plasma leaving the Sun and neutral particles in the exospheres of solar system bodies results in a soft X-ray emission which, if imaged, can help us to understand these interactions of the solar wind with these bodies on large scales. At magnetized bodies, the impact of the solar wind results in global deformations of planetary magnetic fields and physical processes at kinetic, fluid and global scales that capture and energise particles within magnetospheres which ultimately deposits energy into planetary ionospheres and atmospheres. While in-situ measurements have provided deep insights into small-scale processes in these regions, the global configuration of the system remains elusive, revealed only through simulation or climatological empirical models. A new joint mission between the European Space Agency (ESA) and Chinese Academy of Sciences (CAS) will provide a unique global view of our near-Earth space environment, enabling us understand the links between the Sun, magnetosphere and ionosphere. Due for launch in late 2025, the SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission is a novel endeavour to observe the coupling of the solar wind with the magnetosphere through to the ionosphere. To do this, SMILE will remotely sense the magnetosheath and cusps through X-ray emissions from solar wind charge exchange – a process by which neutral particles in Earth’s exosphere exchange charges with highly charged heavy solar wind ions. SMILE is a self-standing mission, that takes its own in situ measurements of the solar wind and magnetosheath plasma and magnetic field input into the magnetosphere, as well as crucial far ultraviolet observations of the entire northern hemisphere auroral oval to explore the link between the solar wind, magnetosphere and ionosphere. In this talk, we will present the underlying science of the SMILE mission as well as the latest mission developments from ESA, CAS and the international instrument teams. We will also highlight possible synergies with existing missions and ground-based facilities, enabling global and local plasma processes to be studied in unprecedented detail and context.
How to cite: Forsyth, C. and the SMILE mission team: Unique Global Viewing of Earth’s Dynamic Magnetosphere with the Solar Wind – Magnetosphere – Ionosphere Link Explorer (SMILE), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10651, https://doi.org/10.5194/egusphere-egu25-10651, 2025.
The soft X-ray imager (SXI) on board the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission will measure X-rays emitted in the Earth’s magnetosheath and cusps. Using these measurements, we will find the magnetopause positions and shape for variable solar wind conditions. However, the recently developed methods of magnetopause finding do not accurately consider the differences in magnetosheath configuration for northward and southward IMF. Analysing MHD results, we show that the plasma depletion layer occurring in the magnetosheath close to the magnetopause for a northward IMF may shift the maximum of X-ray emission farther from the Earth. It requires corrections in calculations of the magnetopause position obtained from the maximum integrated X-ray emissivity.
How to cite: Samsonov, A. and Forsyth, C.: Finding magnetopause standoff distance for different IMF clock angles: application for the forthcoming SMILE mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11609, https://doi.org/10.5194/egusphere-egu25-11609, 2025.
In the Earth’s magnetotail fast earthward plasma flows (so-called Bursty Bulk Flows) are often associated with dipolar magnetic flux bundles. The leading edges of such earthward-moving flux bundles are called dipolarization fronts (DF). Previous studies have reported wave signatures around the local proton cyclotron frequency during selected events, using data from the Cluster, THEMIS and MMS missions. In the present study, we examine characteristics of these ion-scale waves during several hundred DF events, observed by NASA’s Magnetospheric Multiscale mission (MMS) between 2017 and 2022. By applying a wavelet analysis to the database, we not only obtain a statistical picture of the waves from spectral parameters such as the polarization, propagation direction, and electromagnetic character. It also allows us to map their temporal distribution around the DFs, and to obtain a global picture about the occurrence of such waves across different regions of the magnetotail, including the central plasma sheet, the outer plasma sheet, and the plasma sheet boundary layer. Based on the analysis we discuss possible generation mechanisms of the waves.
How to cite: Hosner, M., Nakamura, R., Schmid, D., and Panov, E.: Statistical Survey of Ion Cyclotron Wave Signatures around Earth's Magnetotail Dipolarizations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11479, https://doi.org/10.5194/egusphere-egu25-11479, 2025.
Auroral spirals have different morphologies and origins. In this study, we propose a possible mechanism for the formation of an eastward-moving auroral spiral, which was observed in Tromsø, Norway, during the expansion phase of a substorm on 18 September 2013. During this time, the Cluster and THEMIS-A spacecraft were located ∼7 RE duskward of the spiral generator region in the magnetotail. Prior to the spiral observation, concurrent magnetic field dipolarizations, bursty bulk flows and electron injections were measured by the Cluster satellites. At the same time, a local Kelvin-Helmholtz-like vortex street in the magnetic field was detected, which was likely caused by the bulk flows. The vortex street presumably propagated towards the source region of the spiral due to a high dawnward velocity of the flow bursts. The observations suggest that the spiral may have been generated by an associated vortex mapped along the magnetic field lines to the ionosphere. Future research of the generation of auroral spirals requires higher resolution monitoring of the ionosphere.
How to cite: Kronberg, E., Maetschke, K., Partamies, N., and Grigorenko, E.: A possible mechanism for the formationof an eastward moving auroral spiral, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10731, https://doi.org/10.5194/egusphere-egu25-10731, 2025.
The Cluster mission consists of 4 identical spacecraft, each carrying 11 scientific experiments. The spacecraft were launched in July and August 2000 into near polar inclined, 19x4 RE elliptic orbits. All four spacecraft have been in operation until September 2024. The magnetosphere environment is highly dynamic and its regions cannot be accessed by the orbital information alone. The purpose of the Geospace Region and Magnetospheric Boundary identification (GRMB) dataset is to provide information on the regions crossed by each of the 4 Cluster spacecraft.
The dataset includes 15 different labels, among them: plasmasphere, plasmapause transition region (TR), plasmasheet TR, plasmasheet, lobes, polar regions, magnetopause TR, magnetopause, magnetosheath, bow shock TR, and solar wind and foreshock. The 4 remaining labels are: inside the magnetosphere, outside the magnetosphere, unknown, and no available data. Transition regions can include properties matching the surrounding regions. For example, a bow shock TR can include short periods of solar wind or magnetosheath. Solar wind and magnetosheath should not include bow shock crossings.
The GRMB dataset is based on more than 40 Cluster data products available at CSA, taken from 7 instrument suites. The methodology relies on the visual identification of the boundaries between two consecutive GRMB items. The methodology does not define what is a bow shock or what is a magnetopause, for example. The goal is to have labeled regions that contain the bow-shocks or magnetopauses. And then each user can apply its own definition on the appropriate label subset.
In this study we present the different localization of the different regions based on the GRMB dataset. The properties (plasma density, plasma velocity, magnetic field, …) of different regions are also investigated to show the benefit of this dataset to perform scientific studies.
This dataset is now available at the Cluster Science Archive (CSA) for the years 2001-2022.
How to cite: Grison, B., Darrouzet, F., Maggiolo, R., Hajoš, M., and Taylor, M.: Localization of the Cluster satellites in geospace with the publicly available GRMB (Geospace Region and Magnetospheric Boundary) dataset, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5258, https://doi.org/10.5194/egusphere-egu25-5258, 2025.
Following 24 years of space operations, during which the Cluster spacecraft have greatly advanced our understanding of the dynamics of the Earth’s magnetosphere and its interaction with the solar wind, the first of the four-spacecraft performed a controlled re-entry into the Earth’s atmosphere in September 2024. The CIS (Cluster Ion Spectrometry) experiment has been one of the spearheads of the Cluster mission, with more than 1300 science papers published, based on the analysis of the data provided by this experiment. Major breakthroughs were possible in topics such as collisionless shocks, boundary layers, substorm development, auroral physics, the dynamics of the plasmasphere, ionospheric ion outflow and escape, ring current dynamics, or extreme space weather events. All the high-resolution CIS data are archived and publicly available at the Cluster Science Archive (https://csa.esac.esa.int).
How to cite: Dandouras, I. and the CIS Team: Highlights of the Cluster Ion Spectrometry (CIS) experiment, following 24 years of successful operation , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12118, https://doi.org/10.5194/egusphere-egu25-12118, 2025.
The radiation belts of the Earth and magnetised planets include high energy electrons reaching energies of up to 50 MeV. Observations at the Earth show that the electron flux is highly variable, and that acceleration must take place inside the planetary magnetic field. Soon after the radiation belts were discovered it was thought that inward radial diffusion was the main process responsible for the acceleration, but it was difficult to reproduce the timescale for some of the observed variations in the electron flux. Local electron acceleration via Doppler shifted cyclotron resonance with chorus waves was proposed as an alternative mechanism and has been shown to play a major role in forming the outer electron belt at the Earth reaching energies of several MeV. Here we review some of the evidence for local acceleration and describe the process of chorus wave acceleration at the Earth. We review other types of plasma waves, such as magnetosonic waves, that could contribute to electron acceleration and describe the conditions necessary to reach electron energies of several MeV. We show examples of chorus and other types of plasma waves at Jupiter and Saturn and show how they play an important role in accelerating electrons to form the radiation belts at those planets. We suggest that wave acceleration is the missing link in a set of process that starts with volcanic gasses from the moon Io and results in the emission of synchrotron radiation from Jupiter. We suggest that wave acceleration is a universal process operating at the magnetised planets. Finally, we show how wave acceleration is included into space weather forecasting models to help ensure the safe and reliable operation of satellites on orbit around the Earth.
How to cite: Horne, R.: Electron Acceleration by Wave-Particle Interactions at the Earth and Magnetised Planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11783, https://doi.org/10.5194/egusphere-egu25-11783, 2025.
We report the total electron content (TEC) perturbations due to a G3 solar storm of the solar cycle 25. Measurements from 4 GPS stations over the East Antarctica, along ~70 S, are studied. A magnitude enhancement of 37.15% was seen in Syowa at 39E geo longitude. On the next day, TEC depleted by 55.55% magnitude. The other stations, Mawson at 62E, Bharati at 76E, and Davis at 77E, also report similar perturbations. The longitudinal propagation of the storm effect along a polar cusp latitude is presented. The depletion in TEC is further discussed as the recovery phase of the thermosphere.
How to cite: Dube, A., Singh, A., Rawat, R., and Saini, S.: Characteristics of TEC at the polar cusp latitudes of Antarctica during the ascending phase of solar cycle 25, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20031, https://doi.org/10.5194/egusphere-egu25-20031, 2025.
Electrons precipitate into the Earth’s atmosphere from magnetospheric plasma regions as a continuously varying flux. Energetic electron precipitation (EEP) forms reactive odd nitrogen (NOX) and hydrogen (HOX) oxides which catalytically destroy ozone in the high-latitude thermosphere and mesosphere. Moreover, during polar darkness, the NOX radicals formed by EEP descend to the stratosphere and spread the EEP effect down to the wintertime polar middle atmosphere. Several studies have shown that EEP affects the temperature in the polar middle atmosphere and the strength of the polar vortex, a westerly wind system around the winter pole. The EEP effect is strong in the northern hemisphere but has so far remained unclear in the southern polar vortex. Here we examine the EEP effect on the chemical and dynamical features of the mesosphere and stratosphere both in the northern and southern hemisphere using satellite observations of the EEP by POES/MEPED and atmospheric parameters by Aura/MLS. We also utilize the geomagnetic aa index as a proxy for EEP and the ERA5 reanalysis dataset for atmospheric variables to extend the temporal coverage of observations. We show that, while the effect of EEP on the polar vortex is stronger in the northern than southern hemisphere, the EEP also affects the southern polar vortex in the late winter and spring. This is, e.g., seen in the timing of the final warming.
How to cite: Salminen, A., Asikainen, T., and Mursula, K.: Impact of energetic electron precipitation on the northern and southern polar vortex, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6170, https://doi.org/10.5194/egusphere-egu25-6170, 2025.
Omega bands are mesoscale auroral structures that appear as eastward-moving poleward protrusions of the auroral oval. Typically, omega bands are observed in the post-midnight sector during geomagnetically active periods, and are associated with pairs of upward- and downward-aligned field aligned currents connecting to the magnetotail outside the geostationary distance. The magnetospheric or solar wind drivers of these dynamic structures are not well understood.
Recent analysis of 28 omega band events identified with THEMIS ASI between 2006 and 2013 shows that omega bands are associated with compression regions in the solar wind (Cribb et al., 2024). Analysis of 200 omega band events identified with the MIRACLE network between 1996 and 2007 yields similar results, highlighting the role of high solar wind density in driving the auroral activity. Here we complement the solar wind observations with GOES measurements from geostationary orbit and ground magnetic observations from the SuperMAG database to identify magnetosphere-ionosphere coupling processes that occur during these intervals. Our results will shed light on how solar wind-magnetosphere-ionosphere coupling processes operate during medium to strong geomagnetic storms.
How to cite: Cribb, V., Pulkkinen, T., Gallardo-Lacourt, B., Kepko, L., and Partamies, N.: Auroral omega bands: Solar wind drivers and role in storm and substorm processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2952, https://doi.org/10.5194/egusphere-egu25-2952, 2025.
The study of the space radiation environment surrounding Earth is a fundamental aspect of space weather research, as high-energy particles pose a significant threat to the electronics on every single launched satellite. The gap between Van Allen's outer and inner electron radiation belts is filled by the high-energy electrons shifted radially inward from the outer belt due to a variety of physical mechanisms. They comprise geomagnetic storms, interactions between sub-relativistic particles, and electromagnetic emissions of both natural and artificial origin.
Recent advancements in this field have led to the discovery of a third persistent electron radiation belt at L ~ 1.6 as identified by the STEP-F instrument (Dudnik et al., 2022). Furthermore, empirical evidence suggests that the medium-scaled variations of ionospheric total electron content (TEC) at the middle latitudes can be associated with sporadic microbursts of high-energy electrons below Van Allen radiation belts and within the gap separating inner and outer belts. These findings underscore the necessity of continuous and precise monitoring of the near-Earth radiation environment.
In this study, we introduce the initial concept of the Particle Instrument for Combined Analysis of Space Environment (PICASE) will be designed in a frame of ESA’s Space Weather Nanosatellites System (enhancement study) initiative. The suite intends for uninterrupted monitoring of the high-energy electron and proton fluxes in low Earth orbit (LEO). The instrument is being designed to achieve high energy and time resolution, enabling detailed comparative analyses of charged particle dynamic energy spectra within the Van Allen radiation belts, and in microbursts occurring outside the belts and the South Atlantic Anomaly.
The methodological approach of PICASE involves the determination of particle sort, precise determination of individual particle energies, separately for electrons and protons, and accumulation of particle counts within a predefined aperture. To generate dynamically changed radiation maps across various energy at satellite altitudes we expect continuous, full-day measurements. To distinguish trapped and precipitating particles, and those induced by human activities and ionospheric storms from each other the instrument will incorporate three detector heads equipped with large-area active sensors. Expected technical characteristics and structural block scheme of PICASE are presented too.
This work is supported by the “Long-term program of support of the Ukrainian research teams at the Polish Academy of Sciences carried out in collaboration with the U.S. National Academy of Sciences with the financial support of external partners”.
This research was carried out in collaboration with the European Space Agency (ESA), under contract 4000146628/24/D/SR.
Reference.
O.V. Dudnik, J. Sylwester, M. Kowaliński, P. Podgórski, K. J.H. Phillips. Detection of the third innermost radiation belt on LEO CORONAS-Photon satellite around 2009 solar minimum. Advances in Space Research, 2022. Vol. 70, pp.1441–1452.
How to cite: Dudnik, O., Kowaliński, M., Bąkała, J., Podgórski, P., Ścisłowski, D., and Kurbatov, E.: The PICASE suite for radiation space weather monitoring at LEO: initial concept, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10917, https://doi.org/10.5194/egusphere-egu25-10917, 2025.
Over the past decades, numerous observations and model studies have provided substantial evidence that space weather, through particle precipitation, affects the chemistry and dynamics of the stratosphere. Concurrently, the significance of stratospheric dynamics, particularly in winter short-range and seasonal forecasts, has been highlighted. However, there has been little effort to integrate the knowledge from these two research fields.
This review aims to bridge the gap between the Space Physics and Climate research communities. It will elucidate current knowledge on Energetic Particle Precipitation (EPP) and its impact on the chemistry and dynamics of the mesosphere and stratosphere, highlighting recent research. Additionally, it will present scientific findings demonstrating that EPP forcing of the stratosphere can migrate downwards into the troposphere and reach the surface. Particularly during the QBO-E phase and/or close to a sudden stratospheric warming (SSW), EPP can significantly impact stratospheric dynamics projected onto the North Atlantic Oscillation (NAO) or Northern Annular Mode (NAM). The review proposes EPP as a potential moderator of sudden stratospheric warmings (SSWs) in terms of their occurrence, timing, and strength, which are crucial parameters for short-range and seasonal forecasts for the Northern Hemisphere (NH) in winter. Moreover, it presents research demonstrating that the EPP chemical-dynamical coupling is becoming stronger in an atmosphere influenced by climate change. Bridging the gap between space physics and climate research is essential, as the natural variability of the atmosphere underpins the climate signal. Better prediction of SSWs and their effects on the northern winter weather is crucial preparing for extreme weather events and supporting economic activities. This interdisciplinary approach can enhance our overall understanding of the Earth’s atmosphere and its complex processes.
How to cite: Nesse, H., Asikainen, T., Decotte, M., Funke, B., Harvey, L., Huixin, L., Jia, J., Liu, H., Maliniemi, V., Partamies, N., Salice, J., Salminen, A., Seppälä, A., and Stephan, C.: Why space weather is important for climate research and seasonal forecasting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15379, https://doi.org/10.5194/egusphere-egu25-15379, 2025.
During geomagnetic storm, large fluxes of energetic particles can precipitate into the Earth’s atmosphere and causes excess ionization therein [Ni et al., GRL, 35, 11, 2008], ultimately leading to the depletion of polar ozone layer. The subionospheric Very Low Frequency (VLF, 3-30 kHz) technique has been widely utilized to study those space weather events that influence the D-region ionosphere, including electron precipitation from the radiation belts [Inan, GRL, 17, 6, 1990; Rodger, RG, 37, 317, 1999; Clilverd et al, RS, 36, 773, 2001]. However, most studies were devoted to the analysis of VLF measurements during one or several geomagnetic storms. Few statistical studies have been conducted and how VLF signals respond to geomagnetic storms, especially near the South Atlantic Anomaly (SAA) region, is insufficiently investigated.
In this study, we use the VLF data collected by the receiver developed by Wuhan University, and installed at the Great Wall Station (GWS) in Antarctica. We mainly focus on the measurements of VLF signals from the NAA, NPM, NML, and NLK transmitters, and a total of 18 moderate and strong geomagnetic storms between 2022 and 2023 have been investigated. The path from NAA to GWS is particularly noteworthy since it crosses the SAA region. Our results show that the disturbance caused by geomagnetic storms mainly occurred at sunset or during nighttime conditions, with an amplitude change of 5.3 dB during nighttime conditions and 6.1 dB during sunset. The disturbance typically ~last for 1.5 hours, and the maximum change of VLF amplitude typically occurred several hours after the minimum value of Dst index, with an average delay of 5 hours. The disturbance last for 1.5 hours and was not well correlated with the Dst index. The disturbances are likely caused by energetic particles within the drift loss cone angle that precipitate into the SAA region.
How to cite: Cheng, W., Xu, W., Gu, X., Ni, B., Wang, S., Feng, J., Ma, W., Shi, H., Xu, H., Zhai, D., and Pan, Y.: A Statistical Study of VLF Measurements during Geomagnetic Storms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19871, https://doi.org/10.5194/egusphere-egu25-19871, 2025.
The geomagnetic disturbance index SYM-H is primarily governed by the total kinetic energy of ring current particles. Consequently, the energy balance mechanism of the ring current provides a foundation for constructing an SYM-H evolution equation for predictive purposes. This study builds upon a modeling approach introduced by Ji et al. (2023) to develop an algebraic equation for predicting the SYM-H index based on the equilibrium between energy injection and ring current loss. A fully connected neural network determines the loss term in the model, while the energy injection function is derived from established solar wind–magnetosphere energy coupling functions, with its scale factor treated as a free-fitting parameter to optimize observational predictions. The model, trained on solar wind and SYM-H data from 20 magnetic storms, effectively predicts the SYM-H index one and two hours in advance, achieving root mean square errors (RMSE) of 6.7 nT and 8.9 nT, respectively. These results reflect a 7% improvement for the 1-hour model and a 6% improvement for the 2-hour model compared to the previous version. Moreover, the scale factors for the solar wind parameters in the energy coupling function align with prior observations of the magnetotail current sheet, reinforcing the conclusion that the ring current energy predominantly originates from the current sheet. The neural network-determined lifetimes of ring current particles vary with the SYM-H index, approximating six hours during the fast recovery phase and exceeding 10 hours in the slow recovery phase. This variation is consistent with a transition in dominant ring current particles from oxygen ions to protons during intense storms.
How to cite: Ma, L.: Predicting the SYM-H index using the ring current energy balance mechanism , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4948, https://doi.org/10.5194/egusphere-egu25-4948, 2025.
The aim of the present study is to deduce the velocity of the plasmapause expansion based on the novel method that we have developed.
For that, we use the dataset of 6800 Plasmapause Positions crossed by the THEMIS spacecraft from 2008 to 2012 (Cho et al., 2015; Bandić et al., 2017). Plasmapause positions were identified from electron density profiles measured by THEMIS satellites.
Within this dataset, we aim at finding satellite plasmapause crossings during quiet geomagnetic activity periods.
The quiet times will be defined based on values of geomagnetic activity index Kp. We will use different cut-off of Kp values with a step of 0.33 up to Kp=3.
The new method and results will be presented.
How to cite: Verbanac, G., Bandić, M., Ivanković, L., and Živković, S.: Expansion velocity of the quiet time plasmapause based on THEMIS satellite, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7239, https://doi.org/10.5194/egusphere-egu25-7239, 2025.
Understanding the helium budget of the Earth’s atmosphere is a longstanding challenge in atmospheric science. In the Earth's atmosphere, the abundance and isotopic composition of helium are shaped by interactions with both the solid Earth and outer space. A recent observation of a temporary excess of 3He in the polar atmosphere has been attributed to solar flares. The solar wind, which has an average helium content of ~5% He++ and a 3He/4He ratio of ~2350—much higher than that of the atmosphere—precipitates mainly in the auroral zone, an oval-shaped region located at high latitudes.
The Earth is a magnetized planet surrounded by a magnetosphere, which acts as an interface between the solar wind and the Earth’s atmosphere. The dayside auroral zone, connected to the magnetospheric cusp, provides a direct path for solar wind precipitation. However, in the remainder of the auroral zone, ion precipitation consists of a mixture of solar wind ions and ionospheric ions that are returned to the Earth's atmosphere.
We use 11 years of ion precipitation measurements from the DMSP satellites, combined with in-situ He measurements in the solar wind (from the OMNI database) and empirical formulas derived from satellite observations of the Earth's magnetosphere, to estimate the 3He and 4He precipitation rates in the Earth's upper atmosphere. We analyze yearly averages and peak fluxes, considering separately the contributions from the dayside auroral zone and the rest of the auroral zone. Additionally, we discuss the locations of He precipitation regions and the effects of solar and geomagnetic activity on the precipitating He flux.
Our results show that auroral precipitation is a significant source of atmospheric 3He, comparable to outgassing from the Earth’s core. However, they suggest that solar-flare-associated 3He precipitation alone is likely insufficient to explain the observed polar excess.
How to cite: Maggiolo, R., De Jonghe, W., Alonso Tagle, M. L., Cessateur, G., and Darrouzet, F.: Helium isotopes precipitation in the Earth’s upper atmosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16189, https://doi.org/10.5194/egusphere-egu25-16189, 2025.
Understanding atmospheric escape over geological timescales is essential for constraining a planet's capacity to retain its atmosphere and sustain life. Earth’s atmosphere has drastically changed in composition, with a significant increase in oxygen occurring during the Great Oxidation Event (GOE) 2.45 Gyr ago. Atmospheric oxygen can be ionized and energized by solar radiation and plasma interactions involving the solar wind, the magnetosphere, and ionosphere, eventually leading to its escape into space either as a neutral or as an O+ ion.
For Earth, the main challenge of this work lies in estimating past escape rates from the extrapolation of present-day observations to the younger solar system environment, since the GOE, when an increase of atmospheric oxygen is observed in the geological record.
To achieve this, we developed a semi-empirical model, that considers seven different escape mechanisms to estimate the time evolution of the average oxygen escape rate. We consider the evolution of the solar wind and solar radiation, the Earth’s magnetic moment, and the Earth’s exosphere while assuming a constant atmospheric composition. The escape rate of each escape mechanism is calculated considering analytical formulas, a physical scaling and/or empirical formulas.
During the last 2.45 Gyr., oxygen escape from Earth was dominated by the escape of oxygen ions through the polar wind and polar cusp escape. We estimate that the past oxygen escape rate was more than one order of magnitude higher than now, reaching a total escape rate above 1027 s-1 at the time of the GOE, and that the total oxygen loss during the last 2.45 Gyr corresponds to 63% of the current atmospheric oxygen content. We discuss the role of key parameters that determine atmospheric escape for a magnetized planet, as Earth.
How to cite: Alonso Tagle, M. L., Maggiolo, R., Gunell, H., Borlina, C., Dandouras, I., de Keyser, J., Evensberget, D., Nichols, C., Vidotto, A., Cessateur, G., Darrouzet, F., and Van Doorsselaere, T.: Evolution of Atmospheric Oxygen Escape from Earth During the Last 2.45 Billion Years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10768, https://doi.org/10.5194/egusphere-egu25-10768, 2025.
The plasma spectrometer JEI is an ion and electron spectrometer designed to observe the thermal and medium energy charged particle environement of Jupiter. It is part of the PEP instrument onboard JUICE. The flyby through the Earth-Moon system in August 2024 was the first test of the instrument in a magnetospheric plasma and under higher radiation. We will report on the instrument performance and on observations of charged particles in the lunar environment and during the crossing of the Earth magnetosphere. JEI was turned on during four short time periods near the moon, in the plasma sphere, and during magnetopause and bow shock crossings in the magnetosheath and back into the solar wind. During the lunar flyby JEi recorded photo electrons accelerated by a highly positive spacecraft potential and effects of spacecraft outgassing. The crossing of the Earth plasmasphere allowed a rare observation of the plasmasphere cold ion composition. This measurement was made possible by the combination of a negative spacecraft potential and a high spacecraft velocity.
How to cite: Fränz, M., Krupp, N., Roussos, E., Fischer, H., Bambach, P., Labudda, R., Wittmann, P., Barabash, S., and Wahlund, J.-E.: Observations of the JUICE PEP JEI plasma spectrometer during theMoon and Earth flyby in August 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17006, https://doi.org/10.5194/egusphere-egu25-17006, 2025.
The long-lasting radial Interplanetary Magnetic Field (rIMF) event has captured the attention of scientists for over two decades because of its unique effect on the magnetosphere. However, our understanding of the structure of this event in the interplanetary space is still limited. Previous studies denote that the traditional approach of shifting the L1 observation into the nose of the bow shock might not be suitable for the rIMF events due to their special orientation. This paper shows our results based on Wind, ACE, and STEREO observations. We estimate the correlation length of solar wind parameters for rIMF and compare it with the values under a Parker-spiral orientation. Moreover, the results show that the average width of the rIMF events in the YGSE direction reaches hundreds of RE.
How to cite: Pi, G., Nemecek, Z., and Safrankova, J.: The 2D structure of long-lasting quasi-radial IMF event in the near-Earth region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4829, https://doi.org/10.5194/egusphere-egu25-4829, 2025.
Geomagnetic activity of the magnetosphere is contributed by the direct-driven and loading-unloading processes. Since the loading-unloading process for the quiet IMF conditions is minimum, we are allowed to focus on the direct-driven process. Quasi-northward interplanetary magnetic field (IMF) has been well known to be a quiet IMF condition for direct-driven geomagnetic activity of the magnetosphere in contrast to that for a disturbed southward IMF condition. Quasi-radial and near-zero IMF are the other quiet IMF conditions, which were usually less studied in the field of magnetospheric physics. A comparison among the three quiet IMF conditions for which one is for the quietest direct-driven geomagnetic activity has not been performed in the past. Here we use two solar cycles of OMNI solar wind data and the three high-latitude geomagnetic indices (AE, PCN, PCS) to perform the comparison. We find that the quasi-northward IMF condition is the winner. The geomagnetic activity for quasi-radial IMF was never the quietest because of an extra dayside reconnection in addition to a lobe reconnection, contributing more energy into the magnetosphere than the other two quiet IMF conditions do.
How to cite: Shue, J.-H. and Nosé, M.: Which interplanetary magnetic field condition is for the quietest direct-driven geomagnetic activity?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3583, https://doi.org/10.5194/egusphere-egu25-3583, 2025.
Plasma structures with the enhanced dynamic pressure, density, or speed are often observed in the Earth’s magnetosheath. These structures, known as magnetosheath (MSH) jets, can be detected downstream quasi-perpendicular and quasi-parallel bow shocks. The structures are highly turbulent and dynamic, and their properties can change significantly, depending on their location and actual orientation of the interplanetary magnetic field (IMF). Recent hybrid-kinetic simulations by Fatemi et al. (2024) have shown that magnetosheath jets, previously emphasized to be simple geometric forms, are complex and interconnected structures that frequently merging or splitting as they move through the magnetosheath. Furthermore, hybrid simulation results have shown that the plasma surrounding these jets can exhibit flow directions perpendicular to or even sunward relative to the solar wind. This highlights the potential for in situ measurements to resolve these small-scale structures and their peculiarities, thereby providing insights into the applicability of such hybrid-kinetic simulations. In the work, we aim to study such a complex magnetosheath jet structure using multi-point spacecraft measurements (THEMIS/MMS) and to compare them with outputs of hybrid simulations.
How to cite: Grygorov, K., Goncharov, O., Safrankova, J., Nemecek, Z., and Fatemi, S.: On the structure of magnetosheath jets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6580, https://doi.org/10.5194/egusphere-egu25-6580, 2025.
Transient enhancements in the dynamic pressure, density or speed are often observed in the Earth’s magnetosheath. They are known as jets and/or plasmoids and can be registered downstream both quasi-perpendicular and quasi-parallel bow shocks (BS). They travel from the BS through the magnetosheath and disturb the ambient plasma. Using measurements by the Magnetospheric Multiscale (MMS) spacecraft, Goncharov et al. (2020) showed similarities in the plasma properties of the jets and fast plasmoids. However, they pointed out that the different magnetic fields inside the structures suggest that the formation mechanisms are different. On the other hand, the parameters of structures registered close to the BS/magnetopause or in the sub-solar/flank magnetosheath differ. Based on our comparative analysis, we discuss features of jet-like structures, their properties, occurrence, evolution, and relation to the upstream/local parameters.
How to cite: Goncharov, O., Kostiantyn, K., Xirogiannopoulou, N., Safrankova, J., and Nemecek, Z.: Evolution of jet-like structures in different regions of the magnetosheath , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8469, https://doi.org/10.5194/egusphere-egu25-8469, 2025.
Plasma structures with an enhanced dynamic pressure, known as jets are often observed in the Earth’s magnetosheath. These structures are more often detected downstream of the quasi-parallel bow shock, i.e., behind the foreshock. This region is dominated by waves and reflected particles which interact with each other and create different transients. Xirogiannopoulou et al. (2024) found that the subsolar foreshock contains several types of structures with enhanced density or/and magnetic field magnitude - plasmoids, SLAMS and mixed structures. Many previous studies established that some of these foreshock structures can be a source of magnetosheath jets (Raptis et al., 2022). Following these results, we use data collected by the cross-calibrated THEMIS spacecraft and present multi-spacecraft case studies of the connection between the foreshock and magnetosheath structures. According to our observations, we suggest that the generation of magnetosheath jets is associated with some additional mechanism from the ones we know (ex. BS ripples) that is more complicated or the knowledge we have is incomplete.
How to cite: Xirogiannopoulou, N., Goncharov, O., Safrankova, J., and Nemecek, Z.: Connection of the magnetosheath jet with the foreshock activities, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6327, https://doi.org/10.5194/egusphere-egu25-6327, 2025.
The Earth’s magnetopause is the boundary separating the terrestrial and the interplanetary magnetic fields. Variations in solar wind pressure and structures originating from the solar wind or foreshock regions induce constant dynamic motion of this boundary. Furthermore, a high velocity shear between the magnetosheath and magnetospheric plasmas can trigger the Kelvin-Helmholtz instability. All these interactions can lead to the generation of waves on the magnetopause, which can either propagate along the magnetopause towards the nightside or form standing surface waves. These surface waves subsequently excite fluctuations within the ambient plasma on either side of the magnetopause, allowing them to propagate away perpendicular to the magnetopause. According to magnetohydrodynamic (MHD) theory, the amplitude of these waves is expected to decrease exponentially with distance from the boundary.
Utilizing the multi-spacecraft mission Time History of Events and Macroscale Interactions during Substorms (THEMIS), we are able to simultaneously observe surface waves at different distances perpendicular to the magnetopause. Here we present preliminary findings that compare these spacecraft observations with predictions from MHD theory.
How to cite: Pöppelwerth, A., Grimmich, N., Nakamura, R., and Plaschke, F.: Amplitudes of Magnetopause Surface Waves: Comparison of THEMIS Observations with MHD Theory, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11069, https://doi.org/10.5194/egusphere-egu25-11069, 2025.
The magnetopause plays a vital role in the magnetospheric system because it controls the flow of mass, energy, and momentum from the solar wind to the magnetosphere. Variations in upstream solar wind conditions directly affect the magnetopause position, shape, and motion. We propose that the ion speed component aligned with the magnetopause normal direction inside the magnetopause boundary layers should be relate to the magnetopause speed. Our study aims to comprehensively understand the profiles of plasma parameters in the magnetopause boundary layer, and then to find a better method for estimation of the speed of magnetopause motion by using a single-satellite observation. Such a new approach can substantially increase the number of observations of the magnetopause speed and help us to understand the magnetopause motion in more detail.
How to cite: Ghosh, M., Pi, G., Nemecek, Z., and Safrankova, J.: Magnetopause speed vs the ion motion inside the boundary layer , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6617, https://doi.org/10.5194/egusphere-egu25-6617, 2025.
