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 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.