Session ST2.4

[Programme]

ST2.4 | Global magnetospheric dynamics in simulations and observations

Global magnetospheric dynamics in simulations and observations

Convener: Andrey Samsonov | Co-conveners: Yulia Bogdanova, Tianran Sun, Bayane Michotte de Welle, Yann Pfau-Kempf

Orals

| Thu, 01 May, 16:15–18:00 (CEST)

Room 0.16

Posters on site

| Attendance Thu, 01 May, 10:45–12:30 (CEST) | Display Thu, 01 May, 08:30–12:30

Hall X4

Large-scale dynamic processes in different magnetospheric regions, e.g., in the magnetosheath, at the magnetopause, in the outer and inner magnetosphere, magnetotail, ring current and plasmasphere are closely interconnected. The magnetosphere should therefore be considered as a global system. The state of the magnetosphere is controlled mainly by solar wind conditions. The interplanetary magnetic field (IMF) and solar wind velocity govern the energy input into the magnetosphere. However, solar wind properties change when plasma moves through the bow shock and magnetosheath. The magnetic reconnection rate at the dayside magnetopause depends on parameters in the surrounding magnetosheath and magnetosphere rather than directly on the solar wind conditions. Once dayside reconnection starts, magnetic flux accumulates in the magnetotail lobes, eventually resulting in substorms or steady magnetospheric convection. Magnetic reconnection in the magnetotail injects thermal and energetic particles into the inner magnetosphere and downward along magnetic field lines into the ionosphere. The Kelvin-Helmholz instability provides another important mechanism of energy and momentum transition from the solar wind into the magnetosphere.

Global magnetospheric dynamics can be studied by means of increasingly sophisticated numerical simulations (MHD, hybrid, or fully kinetic), with empirical and semi-empirical models, or using multipoint in situ spacecraft observations. A fleet of space missions can investigate magnetospheric phenomena in-situ, providing crucial information concerning the positions and dynamics of the magnetospheric plasma boundaries and the global distribution of the magnetospheric plasma and processes within it. Past and future global imaging missions (e.g., LEXI, SMILE, GEO-X, and others) can complete this picture providing large-scale snapshots of some geospace regions. Accurate modelling of global magnetospheric processes is an essential condition for successful space weather predictions, but sometimes model predictions are very different from each other even for typical solar wind conditions. We welcome any work presenting results on the global dynamics of the Earth’s magnetosphere as well as the magnetospheres of other planets.

Orals: Thu, 1 May, 16:15–18:00 | Room 0.16

Chairpersons: Andrey Samsonov, Tianran Sun, Yulia Bogdanova

16:15–16:20

5-minute convener introduction

16:20–16:30

EGU25-12953

ECS

solicited

On-site presentation

Understanding stormtime geospace as a complex, coupled system: Recent progress from the Center for Geospace Storms

Savvas Raptis, Viacheslav Merkin, Kareem Sorathia, Dong Lin, Shanshan Bao, Anthony Sciola, and Kevin Pham

The Center for Geospace Storms (CGS) is a NASA DRIVE Science Center focused on geospace science. CGS is pursuing the goal of developing an understanding of the stormtime geospace as a complex system exhibiting strong coupling across physical regimes, domains and particle populations, which occurs across disparate spatiotemporal scales. CGS is tackling this problem via a concerted effort using both data analysis from heterogeneous sources (e.g., in situ, remote sensing and ground-based platforms) and physics-based modeling. In particular, the CGS team is developing the Multiscale Atmosphere-Geospace Environment (MAGE) model that couples all the relevant domains of geospace while doing it at sufficiently high resolution to capture key cross-scale interactions. In this presentation, we discuss recent work from the CGS team concentrating on high- to mid-latitude magnetosphere-ionosphere coupling in stormtime geospace. We discuss the novel model of energetic particle precipitation in MAGE, based on gray-box modeling of wave-induced particle precipitation, and its applications to high-resolution modeling of the aurora. We show examples of simulations of mesoscale auroral forms, such as giant undulations, and their connection to inner magnetosphere dynamics, including the subauroral polarization streams. We also review our recent efforts on developing a new high-resolution (in space and energy) inner magnetosphere model. Finally, we conclude the talk by emphasizing the interconnectedness of stormtime geospace using the May’24 superstorm as an example.

How to cite: Raptis, S., Merkin, V., Sorathia, K., Lin, D., Bao, S., Sciola, A., and Pham, K.: Understanding stormtime geospace as a complex, coupled system: Recent progress from the Center for Geospace Storms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12953, https://doi.org/10.5194/egusphere-egu25-12953, 2025.

16:30–16:40

EGU25-17932

ECS

On-site presentation

A new approach to data-model comparisons: Using MAGE and Lompe to unravel ionosphere-magnetosphere electrodynamics

Sara Gasparini, Larry Kepko, Karl Laundal, Viacheslav Merkin, Adam Michael, and Kareem Sorathia

Global numerical simulations are a valuable tool for understanding the Sun-Earth interaction as they provide a more complete picture of the system when compared to typically sparse observations. Yet, comparison of global numerical simulations against observations is complicated by the inherent uncertainty that the observed phenomena occurred at the same time and location in the simulation domain. It is therefore common to use aggregate measures of the Sun-Earth interaction, such as the Dst and AL indices and cross-polar cap potential, with the downside of missing details, especially at the mesoscale lengths. Despite being quantitative, these aggregate measures can also hide important physical processes. It is therefore crucial to find metrics or parameters that provide deeper insight into the physics but do not rely precisely on the location of the observations. Recently, data assimilative models to reproduce patterns of high-latitude ionospheric electrodynamics have been improved, and they can be used to reconstruct ionospheric quantities using observations to compare with simulation outputs, providing a new avenue for data-model comparisons. In this paper, we demonstrate this new approach to data-model comparisons by assimilating global MHD simulation (MAGE) data into Lompe for direct comparison with the real-data-assimilation patterns of field-aligned currents and their ionospheric components (the FAC terms associated with the divergence of the electric field, gradient of the Hall conductance, and gradient of the Pedersen conductance) from \citeA{gasparini2024quantifying}. In addition, we calculate reconnection electric fields for the MHD simulations and real-data assimilation, and find that the nightside reconnection rate from the MAGE simulations is 30% higher than in the real data case. We also find that with the MHD simulation the system enters steady-magnetospheric convection, in contrast to the observations which indicated a classic substorm. We conclude by speculating on the possible sources of discrepancies between the model and observations.

How to cite: Gasparini, S., Kepko, L., Laundal, K., Merkin, V., Michael, A., and Sorathia, K.: A new approach to data-model comparisons: Using MAGE and Lompe to unravel ionosphere-magnetosphere electrodynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17932, https://doi.org/10.5194/egusphere-egu25-17932, 2025.

16:40–16:50

EGU25-5490

Highlight

On-site presentation

Dynamic X-ray Imaging of the Magnetosheath Expected during a Super Storm

Yuqi Gong, Tianran Sun, Binbin Tang, Yihong Guo, Steve Sembay, and Chi Wang

The Earth's magnetosheath is a vital source region of soft X-ray emissions generated by the solar wind charge exchange (SWCX) mechanism in geospace. Soft X-ray imaging provides valuable insights into the overall morphology of the magnetosheath. Nevertheless, the dynamic variations in X-ray images during extreme space weather have not been comprehensively studied. Using a global magnetohydrodynamic code, we simulated the temporal variations of the magnetosphere on 10-11 May 2024, during the most intense geomagnetic storm of Solar Cycle 25. The X-ray images of the magnetosphere during the entire event are presented to assess the response of the magnetosphere to the impact of the coronal mass ejection (CME), with a particular focus on the periods of sudden solar wind number density increase, the southward turning of the interplanetary magnetic field (IMF), and an extreme solar wind condition. With the advent of the Solar Wind-Magnetosphere-Ionosphere Link Explorer (SMILE), a joint mission between ESA and CAS, investigations into the large-scale structure and dynamic evolution of magnetopause will be enabled via global X-ray imaging.

How to cite: Gong, Y., Sun, T., Tang, B., Guo, Y., Sembay, S., and Wang, C.: Dynamic X-ray Imaging of the Magnetosheath Expected during a Super Storm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5490, https://doi.org/10.5194/egusphere-egu25-5490, 2025.

16:50–17:00

EGU25-8724

ECS

On-site presentation

Quantitative estimates of the magnetic flux variations in the inner magnetosphere during an intense storm.

Soboh Alqeeq, Dominique Fontaine, Olivier Le Contel, Mojtaba Akhavan-Tafti, Emanuele Cazzola, and Tsige Atilaw

In the present study, we analyzed the Earth's magnetospheric dynamics in response to the intense geomagnetic storm of 19th December 2015, marked by a substantial decrease in the SYM-H index to -188 nT. We focushere on the variations of the magnetic flux content (MFC) within closed magnetic shells in the inner magnetosphe up to a distance roughly corresponding to the magnetopause. During this event, we had the chance to have observations on the dayside and on the nightside and at different distances in the magnetosphere (OMNI, Van Allen Probes, GOES, THEMIS, MMS, Cluster). Using these various observations together with the Tsyganenko T96 model, we estimated the MFC in the inner magnetosphere. It is found that in comparison to pre-storm conditions, MCF decreased during SSC by 17% and in the main phase by 27% but it gradually rebounded (swelled) during 3 following days of the recovery phase reducing the decrease to 22%, 14% and 8% respectively. The importance of storm-time magnetospheric dynamics in the field of space weather forecasting is emphasized by these findings and calls for further studies.

How to cite: Alqeeq, S., Fontaine, D., Le Contel, O., Akhavan-Tafti, M., Cazzola, E., and Atilaw, T.: Quantitative estimates of the magnetic flux variations in the inner magnetosphere during an intense storm., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8724, https://doi.org/10.5194/egusphere-egu25-8724, 2025.

17:00–17:10

EGU25-16673

ECS

On-site presentation

O+-rich Warm Plasma Cloak in the Dayside Magnetosphere: Nine Years of MMS Observations.

Victor Montagud-Camps, Sergio Toledo-Redondo, Jerry Goldstein, Stephen Fuselier, Mats André, Inmaculada F. Albert, Aida Castilla, Alfonso Salinas, Jorge Portí, and Enrique Navarro

Plasma inside Earth's magnetosphere can have a substantial effect in the efficiency of magnetic reconnection at the magnetopause, specially if it is rich in cold and heavy ions. We have analyzed 9 years of data gathered by the Magnetospheric Multiscale (MMS) mission to locate and characterize one magnetospheric plasma population with such features, the warm plasma cloak (WPC). The WPC has an ion temperature that ranges between tens of eV to a few keV and is mainly composed of electrons, protons, and O+ ions. Our statistical study has shown that 51% of MMS observations in the outer magnetosphere correspond to WPC population, and that 15% of the WPC is rich in O+ ions. The presence of heavy ions in the WPC is related to strong geomagnetic activity. We have found that the detections of O+ rich WPC take place 9 hours after geomagnetic events with Kp index larger than 6. The duration of such time gap is in accordance with the prediction of previous models on the formation of the WPC in the dayside magnetosphere.

How to cite: Montagud-Camps, V., Toledo-Redondo, S., Goldstein, J., Fuselier, S., André, M., Albert, I. F., Castilla, A., Salinas, A., Portí, J., and Navarro, E.: O+-rich Warm Plasma Cloak in the Dayside Magnetosphere: Nine Years of MMS Observations., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16673, https://doi.org/10.5194/egusphere-egu25-16673, 2025.

17:10–17:20

EGU25-3271

On-site presentation

The dynamics of NBZ auroras

Steve Milan, Michaela Mooney, Gemma Bower, Gregory Kennedy, and Benoit Hubert

17:20–17:30

EGU25-9390

ECS

On-site presentation

Solar Wind Influence on Dual-Lobe Reconnection and Horse-Collar Aurora

Gregory Kennedy, Stephen Milan, Gemma Bower, Suzanne Imber, and Michaela Mooney

Horse-collar aurora (HCA) are an auroral formation generated by the geomagnetic reconfiguration during prolonged periods of northward-directed interplanetary magnetic field (IMF). HCA formation has been linked to dual-lobe reconnection (DLR) closing open flux at the dayside magnetopause, resulting in a reversal of the typical ionospheric twin-cell convection pattern and a poleward motion of the dawn and dusk portions of the open/closed field line boundary (OCB). This morphology gives rise to a horse-collar or teardrop-shaped polar cap.

We aim to investigate two key aspects of HCA: a) whether the dim region within the HCA is open flux, and b) whether there exists a correlation between the DLR rate and upstream solar wind parameters. This study uses HCA arc velocity as a proxy measurement for DLR rate, allowing us to infer correlation between IMF parameters and DLR rate.

Far-ultraviolet spectral images from the Special Sensor Ultraviolet Spectrographic Imager instrument on-board the Defense Meteorological Satellite Program spacecraft were used to measure the location of HCA in successive polar passes. At the current stage of the study we find a linear relation between HCA closing velocity and the total IMF magnitude and Bz magnitude. No relation was found between HCA closing velocity and solar wind flow speed or IMF By. The timescale for a full closure of the magnetosphere by DLR was also estimated for the events.

How to cite: Kennedy, G., Milan, S., Bower, G., Imber, S., and Mooney, M.: Solar Wind Influence on Dual-Lobe Reconnection and Horse-Collar Aurora, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9390, https://doi.org/10.5194/egusphere-egu25-9390, 2025.

17:30–17:40

EGU25-11522

On-site presentation

Finding Magnetospheric Dynamics with Observed Imbalances in Earth’s Open and Closed Magnetic Flux

Maria-Theresia Walach, Nithin Sivadas, and Mai Mai Lam

Earth’s magnetosphere is an unstable system. We observe this in many aspects of the system, for example, substorms. A key indicator of the state of the system is the amount of open magnetic flux and the rate at which it is changing. These measures are intimately tied to the driving of the system (i.e. dayside reconnection) but also, the response of the system (i.e. nightside reconnection). When they become imbalanced, extraordinary phenomena such as substorms can dominate magnetospheric dynamics. Understanding when and how these imbalances occur is therefore a key to understanding our magnetosphere.

Using auroral data from the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) spacecraft, we calculate the amount of magnetic flux in the open region of the magnetosphere and the amount of flux in the auroral region. The open flux is indicative of the amount of flux which is convecting towards the nightside and the closed flux in the auroral region is indicative of the amount of magnetic flux which is convecting towards the dayside. Together, the two quantities tell us how much of the magnetosphere is convecting. By investigating the timing of the peaks and troughs in these timeseries, we evaluate when the system is unstable and when day- and nightside reconnection occurs. We study these timeseries statistically and the relation between their peaks and troughs.

Overall, and over long timescales, a balance between day- and nightside reconnection must exist because the amount of magnetic flux in the magnetosphere is finite. On timescales of minutes to 100s of minutes however, we find that imbalances occur. We observe that the magnetosphere can become imbalanced on timescales from minutes to ~3 hours, with the median timescale being 24 minutes. Without consideration of any driving parameter or any other dataset and by simply investigating statistically the convecting magnetic flux content, we find two distinct statistical distributions: one where dayside reconnection is dominant and one where nightside reconnection is dominant. We find that the two show differences in their statistical behaviour, indicating that nightside flux closure can be up to 4 times higher than flux opening.

How to cite: Walach, M.-T., Sivadas, N., and Lam, M. M.: Finding Magnetospheric Dynamics with Observed Imbalances in Earth’s Open and Closed Magnetic Flux, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11522, https://doi.org/10.5194/egusphere-egu25-11522, 2025.

17:40–17:50

EGU25-18731

ECS

On-site presentation

Plasma observations in the distant magnetotail under Northward IMF

Michaela Mooney, Steve Milan, and Gemma Bower

The structure and dynamics of the magnetosphere are significantly different during intervals of northward interplanetary magnetic field (IMF) compared to when the IMF is southward. Under northward IMF, reconnection occurs at higher latitudes tailward of the cusps. High latitude reconnection occurring simultaneously in both hemispheres can close significant amounts of open flux in the magnetospheric lobes resulting in an almost entirely closed magnetosphere and has been linked to characteristic auroral signatures, such as cusp-aligned arcs.

Under northward IMF the magnetosphere becomes dominated by closed magnetic flux with associated trapped particles populations which are thought to provide the source particle population for auroral cusp-aligned arcs (Milan et al., 2023; Mooney et al, 2024). However, the structure and properties of the distant magnetotail under northward IMF are poorly understood. We have performed a statistical analysis of ARTEMIS crossings of the distant magnetotail (X_GSE ~ -60 R_E) between 2011 - 2016 to investigate the magnetic field and plasma characteristics in the magnetotail under northward IMF conditions compared to southward IMF conditions. Under southward IMF, the magnetotail is dominated by magnetic pressure with no significant associated plasma population. However, under northward IMF we find that statistically the central distant magnetotail contains denser, hotter plasma and that the plasma pressure in the magnetotail is typically larger than the magnetic pressure. We suggest that the observed hotter, denser plasma population in the central magnetotail could indicate that the plasma sheet extends down to the distant magnetotail under northward IMF.

How to cite: Mooney, M., Milan, S., and Bower, G.: Plasma observations in the distant magnetotail under Northward IMF, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18731, https://doi.org/10.5194/egusphere-egu25-18731, 2025.

17:50–18:00

EGU25-5222

On-site presentation

Evolution of the flux tube instability parameters in plasma injections at Saturnian magnetosphere

Xuanye Ma, Simon Wing, Jay R. Johnson, Peter Delamere, and Robert Allen

The evolution of the flux tube stability parameters in plasma injections at the Saturnian magnetosphere is reviewed. Plasma injections result from an imbalance in the centrifugal, total pressure gradient, and magnetic tension forces acting on plasma in the magnetosphere. Plasma originating from Enceladus tends to move outward due to centrifugal forces while reconnected flux tubes that are depleted of plasma collapse because of the magnetic tension leading to plasma injections. As the flux tube moves inward and contracts, the ambient density and pressure increase sufficiently to resist further collapse, and the injected flux tube brakes. During this process, the flux tube may also lose its integrity due to particle drifts, which allow the exchange of plasma with adjacent flux tubes so as to bring the flux tube closer to equilibrium and stability so that it is indistinguishable from adjacent plasma. Stability parameters using this energy approach are defined and examined. The results show that the net forces push the plasma moves inward for L>11 and outward for L<8.5, while equilibrium is generally reached for 8.5< L< 11, where L is the equatorial magnetic field crossing measured in Saturnian radii. The evolution of the stability parameters can also apply to Jovian and other fast-rotating planetary magnetospheres.

How to cite: Ma, X., Wing, S., Johnson, J. R., Delamere, P., and Allen, R.: Evolution of the flux tube instability parameters in plasma injections at Saturnian magnetosphere , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5222, https://doi.org/10.5194/egusphere-egu25-5222, 2025.

Posters on site: Thu, 1 May, 10:45–12:30 | Hall X4

Display time: Thu, 1 May, 08:30–12:30

Chairpersons: Andrey Samsonov, Yulia Bogdanova, Bayane Michotte de Welle

X4.107

EGU25-1506

Intense Magnetopause Deformation Induced by an Extreme HFA Event: 3-D Hybrid Simulations and Soft X-Ray Imaging

Zhongwei Yang, Tianran Sun, Xiaocheng Guo, Qinghe Zhang, Can Huang, Fan Guo, Dimitra Koutroumpa, and Chi Wang

The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a joint mission of the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS). Its primary objective is to investigate the Earth's magnetosphere's dynamic response to solar wind (SW) impacts through simultaneous in situ measurements of magnetosheath plasma and magnetic fields, X-ray imaging of the magnetosheath and magnetic cusps, and UV imaging of global auroral distributions. In this study, extremely magnetopause deformations associated with Hot Flow Anomalies (HFAs) are examined using a three-dimensional (3-D) global hybrid simulation. Nonuniform grids are used to enhance the resolution of the magnetosheath. Considering the parameters of SMILE's Soft X-ray Imager, we analyze the integrated soft X-ray intensity along the line-of-sight (LOS) over durations ranging from less than one minute to approximately five minutes. The simulation results demonstrate that: (1) high-speed jets (HSJs) at the leading and trailing edges of the HFA can generate X-ray intensities an order of magnitude stronger than the background magnetosheath, whereas the core region of the HFA corresponds to an X-ray dimming area; (2) a mature HFA can cause the magnetopause to expand outward by several Earth radii, exposing magnetospheric material to the solar wind ahead of the bow shock; (3) in minute-scale integrations, the HFA structure, moving from the northern to the southern hemisphere, can be discerned in the integral images within a duration of less than five minutes, while integrations lasting five minutes or longer smooth out the signal entirely. This study serves as a pre-study for the SMILE mission.

How to cite: Yang, Z., Sun, T., Guo, X., Zhang, Q., Huang, C., Guo, F., Koutroumpa, D., and Wang, C.: Intense Magnetopause Deformation Induced by an Extreme HFA Event: 3-D Hybrid Simulations and Soft X-Ray Imaging, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1506, https://doi.org/10.5194/egusphere-egu25-1506, 2025.

X4.108

EGU25-10293

ECS

Magnetospheric Convection in a Hybrid-Vlasov Simulation

Shi Tao, Markku Alho, Ivan Zaitsev, Markus Battarbee, Urs Ganse, Yann Pfau-Kempf, Lucile Turc, and Minna Palmroth

The Dungey cycle is a fundamental process governing large-scale plasma dynamics in near-Earth space. Traditionally, it has been studied using Magnetohydrodynamic (MHD) simulations and ionospheric observations. However, MHD models often oversimplify the complexities of reconnection dynamics and kinetic processes, while observational data tend to lack sufficient coverage. In this study, we investigate the Dungey cycle in a 3D hybrid Vlasov simulation. We also introduce a new method for quantifying reconnection rates in different Magnetic Local Time (MLT) sectors.

During the simulation, we quantify Dungey cycle motion by using reconnection rates in different MLT sectors and identify azimuthal convection channels on the dawn and dusk flanks, which are modulated by dayside reconnection events. Notably, we observe that the effective length of dayside reconnection fluctuates, even under steady solar wind conditions. Our results further reveal significant deviations from ideal MHD theory, which predicts that plasma flows within the magnetosphere should follow flux tube entropy isocontours. Instead, we demonstrate that plasma flows near reconnection sites and in the twilight zone exhibit more intricate and dynamic patterns, deviating from this idealized alignment.

This work validates the Vlasiator 3D simulation as a powerful tool for studying global plasma convection and provides a novel method of quantifying reconnection rates in simulation, as well as showing new results of azimuthal convection channels. Future work should focus on identifying the kinetic processes driving deviations in the alignment of plasma convection with flux tube entropy isocontours between MHD theory and the kinetic approach.

How to cite: Tao, S., Alho, M., Zaitsev, I., Battarbee, M., Ganse, U., Pfau-Kempf, Y., Turc, L., and Palmroth, M.: Magnetospheric Convection in a Hybrid-Vlasov Simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10293, https://doi.org/10.5194/egusphere-egu25-10293, 2025.

X4.109

EGU25-4690

OpenGGCM simulation of Diamagnetic Cavities in the wake of Flux Transfer Events

(withdrawn after no-show)

Shiva Kavosi

X4.110

EGU25-14896

ECS

Ionosphere Plasma Response to Magnetopause X-line Evolution for Ideal MHD

Wei Zhang, Toshi Nishimura, Yuxi Cheng, Paul Cassak, Gang Kai Poh, and Nozomu Nishitani

Magnetic reconnection plays a fundamental role in transporting energy, momentum, and plasma from the solar wind to the magnetosphere-ionosphere system. During an IMF southward turning, a magnetopause reconnection X-line forms near the magnetic equator region and is considered to drive dayside plasma convection in the magnetosphere-ionosphere system. However, how the azimuthal size of flows at the X-line and in the ionosphere relate to each other, and what mechanisms control the azimuthal flow size remain unclear. In this study, we use the global ideal MHD simulation to address this question using an event during an IMF southward turning. The results reveal that after an IMF southward turning, a strong and localized plasma flow channel emerges near noon in the ionosphere. Interestingly, the flow at the magnetopause X-line is azimuthally much wider than the ionospheric flow. The flow becomes narrower as the flow moves toward the cusp. The narrow flow is not created at the X-line region but is driven by azimuthally localized force directed anti-sunward and toward noon. These findings indicate that dayside ionospheric convection is not solely driven by X-line processes but is instead a result of the forces along the magnetopause and in the cusp. This finding underscores the importance of considering global force distributions when examining reconnection-driven plasma dynamics.

How to cite: Zhang, W., Nishimura, T., Cheng, Y., Cassak, P., Poh, G. K., and Nishitani, N.: Ionosphere Plasma Response to Magnetopause X-line Evolution for Ideal MHD, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14896, https://doi.org/10.5194/egusphere-egu25-14896, 2025.

X4.111

EGU25-14798

Dynamic response of cusp boundaries to IMF southward turning: global MHD simulation

(withdrawn after no-show)

Tianran Sun

X4.112

EGU25-8226

ECS

Latitude Variations of Cusp-Related Boundaries Dependent on Solar Wind Conditions and Dipole Tilt: MHD Simulations and Auroral Observations

Huixuan Qiu, Andrey Samsonov, and Yulia Bogdanova

The magnetospheric cusps are populated by the magnetic field lines that connect upward to the magnetosheath and extend downward to the ionosphere, therefore the magnetosheath plasma has direct access to the polar ionosphere in these regions. The location of the cusp responds dynamically to solar wind conditions and geomagnetic field, influencing magnetosphere-ionosphere coupling. The equatorward boundary of the cusp is adjacent to the low-latitude boundary layer (LLBL)/cleft, where the dayside open-closed boundary (OCB) is typically located. The polar cap boundary (PCB) delineates the extent of open magnetic flux, and its midday position is associated with the cusp and OCB. Particles precipitating in the cusp contribute to midday auroral emissions and field-aligned currents. The latitude of midday auroral equatorward boundary varies with the cusp's equatorward boundary, OCB, and the thickness of the LLBL. Field-aligned currents connect magnetospheric currents with ionospheric currents, with the Region 1 currents observed on both open and closed field lines. Consequently, the Region 1 current's high-latitude boundary near local noon relate to the cusp’s equatorward boundary dynamics. Despite the known associations between these cusp-related boundaries, their dynamic responses to variations in solar wind parameters and dipole tilt have not been fully characterized. This study investigates the latitude variations of midday auroral equatorward boundary, OCB footprint in the ionosphere, PCB, Region 1 current poleward boundary, utilizing DMSP auroral observations and CCMC MHD simulation results. The analysis reveals that:

All boundaries shift equatorward with increasing southward IMF B_z, consistent with enhanced dayside reconnection.
The boundaries exhibit systematic responses to IMF B_y and solar wind velocity, reflecting asymmetric convection and magnetospheric compression.
All boundaries in the Northern Hemisphere shift with dipole tilt.
The latitude of the midday auroral lowest-latitude boundary shows seasonal variations and solar cycle dependence.

These findings provide insights into the dependence of cusp location on solar wind conditions and dipole tilt, as well as the dynamic relationships between cusp-related boundaries, emphasizing the cusp’s role in solar wind-magnetosphere-ionosphere coupling.

How to cite: Qiu, H., Samsonov, A., and Bogdanova, Y.: Latitude Variations of Cusp-Related Boundaries Dependent on Solar Wind Conditions and Dipole Tilt: MHD Simulations and Auroral Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8226, https://doi.org/10.5194/egusphere-egu25-8226, 2025.

X4.113

EGU25-4825

Magnetospheric Response to the Mother’s Day Weekend Geomagnetic Storm: Observations from Geostationary Satellites

Sheng Li, Gilbert Pi, Zdenek Nemecek, and Jana Safrankova

The Mother’s Day weekend geomagnetic storm during 10-11 May 2024 is one of the most intense events in recent decades. At least two interplanetary coronal mass ejections (ICMEs) erupted from the active region 13664 on 8 May stacked together, causing the shock observed at the L1 point on 10 May at 17:05 UT. In this study, we utilized geostationary orbit satellite observations to investigate the disturbance of magnetic fields and particles inside the Earth’s magnetosphere. There are four significant findings in this study. First, the subsolar magnetopause had already compressed from about 11.7 R_E (at 13:18 UT) to 8.6 R_E (at 16:59 UT) before the shock arrival, which THEMIS-A observed, then compressed below 6.6 R_E (i.e., geostationary orbit) because of the ICME. Second, Magnetospheric Particle Sensors onboard GOES-16 and GOES-18 detected proton flux increases inside the magnetosphere from about 15:00 UT before the shock arrived. Third, the Energetic Heavy Ion Sensor onboard the GOES-16 and GOES-18 satellites detected helium flux increases on 10 May at about 14:09 and 14:44 UT, respectively. Fourth, the GOES magnetometer recorded the southward magnetic field B_Z on 11 May when the two satellites were in the tail region.

How to cite: Li, S., Pi, G., Nemecek, Z., and Safrankova, J.: Magnetospheric Response to the Mother’s Day Weekend Geomagnetic Storm: Observations from Geostationary Satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4825, https://doi.org/10.5194/egusphere-egu25-4825, 2025.

X4.114

EGU25-13726

ECS

Large-Scale MMS Survey using Rapid Unsupervised Detection of Events (RUDE) Methodology

(withdrawn after no-show)

Matthew Finley, Miguel Martinez-Ledesma, Matthew Blandin, Alex Hoffmann, William Paterson, Matthew Argall, David Miles, John Dorelli, and Eftyhia Zesta

X4.115

EGU25-6363

Throat Aurora and 15MLT-PCA

De-sheng Han and Hui-Xuan Qiu

Throat aurora: The solar wind interacts with the magnetosphere to generate auroras. Auroras primarily occur in a ring-shaped region centered on the geomagnetic poles, known as the auroral oval. Throat aurora is a particular auroral form frequently observed in the dayside ionospheric convection throat region. The throat auroras have been confirmed to be correspondent to magnetopause crack. Based on the observational facts of throat aurora, we suggest that throat aurora should be correspondent to a particular magnetopause reconnection that is radially developed toward the Earth at a rather local region.

15MLT-PCA: The area enclosed by the auroral oval is called the polar cap region. Auroras often occur within the polar cap region as well, including two main types: arcs and patches. This report focuses on the auroral phenomena occurring on the dayside within the polar cap region. These phenomena have been given various names in past research, such as Cusp spot, HiLDA, 15MLT-PCA, and space typhoon. Although these phenomena have distinct observational characteristics, they also share many similarities. In the past, scholars often argued over what to call specific dayside polar cap auroral events, and there has been no clear discussion on the intrinsic connections between these phenomena. Recently, by integrating previous research, we proposed a unified model for these phenomena. In simple terms, it is believed that these phenomena represent different manifestations of tail reconnection on the aurora under different clock angle conditions. This report will briefly introduce the model and discuss its implications for understanding certain issues such as the dawn-dusk asymmetry of space processes and inter-hemispheric asymmetry.

How to cite: Han, D. and Qiu, H.-X.: Throat Aurora and 15MLT-PCA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6363, https://doi.org/10.5194/egusphere-egu25-6363, 2025.

X4.116

EGU25-4022

Jump-Diffusion Modeling of the Auroral Electrojet AL Index: Unveiling Complexity and Criticality

Giuseppe Consolini, Simone Benella, and Paola De Michelis

The Earth’s magnetosphere displays complex and nonlinear dynamics in response to solar wind changes. In the past, some attempts to model the magnetospheric global dynamics as monitored by geomagnetic indices, in terms of stochastic differential equations (SDEs) have been carried out. These studies are important to assess the role of stochastic fluctuations and burstiness in the dynamics of the magnetosphere-iononosphere system.

Here, we present a jump-diffusion model to describe the auroral electrojet AL index, which constitutes a key geomagnetic measure of polar ionospheric currents during substorms. The proposed model employs a jump-diffusion stochastic differential equation (SDE) to capture the nonlinear, intermittent, and scale-invariant behavior of the AL index. Comparison with observations highlights the model capability to reproduce key statistical features of the AL index, such as scaling exponents and burst distributions. However, since the stochastic process involved in our model is Markovian, the model does not have information about the external driving (solar wind) and further efforts are therefore required to include long-range correlations. The relevance and limitations of these approaches in modeling the magnetospheric response are finally discussed.

How to cite: Consolini, G., Benella, S., and De Michelis, P.: Jump-Diffusion Modeling of the Auroral Electrojet AL Index: Unveiling Complexity and Criticality, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4022, https://doi.org/10.5194/egusphere-egu25-4022, 2025.

X4.117

EGU25-15773

ECS

Vorticity in the magnetospheric transition region of a global hybrid-Vlasov simulation

Venla Koikkalainen, Minna Palmroth, Maxime Grandin, Emilia Kilpua, Ivan Zaitsev, Liisa Juusola, Abiyot Workayehu, Giulia Cozzani, Lauri Pänkäläinen, Markku Alho, Konstantinos Horaites, Shi Tao, Jonas Suni, Yann Pfau-Kempf, and Urs Ganse

The transition region between the Earth's dipole field and the stretched magnetotail is a highly dynamic region of space where a variety of complex physical phenomena occur. The aim of this study is to understand the formation and evolution of large-scale plasma flow vortices in the transition region. The vorticity is found in the global magnetospheric hybrid-Vlasov model Vlasiator, which now features an ionospheric solver, enabling the study of magnetosphere-ionosphere coupling. We compare the results of the simulation to other magnetospheric simulations and observations of similar phenomena.

The vortices are highly structured and spread over the nightside with an azimuthal wavelength of about 3.5 RE (Earth radii). The vorticity in the magnetotail is induced by reconnection resulting in Earthward bulk flow with properties similar to bursty bulk flows (BBFs). In addition to BBF-like signatures, we observe that the features of the event are consistent with it originating from the ballooning/interchange instability, in combination with the fast Earthward flow. The fast flows and vorticity in the magnetosphere map onto the ionospheric grid of the simulation, and it can be seen that the Earthward flows create field-aligned currents. Our study investigates the formation of the vortices in the magnetotail, and the resulting ionospheric effects.

How to cite: Koikkalainen, V., Palmroth, M., Grandin, M., Kilpua, E., Zaitsev, I., Juusola, L., Workayehu, A., Cozzani, G., Pänkäläinen, L., Alho, M., Horaites, K., Tao, S., Suni, J., Pfau-Kempf, Y., and Ganse, U.: Vorticity in the magnetospheric transition region of a global hybrid-Vlasov simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15773, https://doi.org/10.5194/egusphere-egu25-15773, 2025.

X4.118

EGU25-83

Contribution of patchy reconnection to the ion to electron temperature ratio in the Earth’s magnetotail

Chuxin Chen and Chih-Ping Wang

The ion-to-electron temperature ratio is a good indicator of the processes involved in the plasma sheet. Observations have suggested that patchy reconnection and the resulting earthward bursty bulk flows (BBFs) transport may be involved in causing the lower temperature ratios at smaller radial distances during southward IMF periods. In this paper, we estimate theoretically how a patchy magnetic reconnection electric field can accelerate ions and electrons differently. If both ions and electrons are non-adiabatically accelerated only once within each reconnection, the temperature ratio would be preserved. However, when reconnection occurs closer to the Earth where magnetic field lines are shorter, particles mirrored back from the ionosphere can cross the reconnection region more than once within one reconnection; and electrons, moving faster than ions, can have more crossings than do ions, leading to electrons being accelerated more than ions. Thus as particles are transported from tail to the near-Earth by BBFs through multiple reconnection, electrons should be accelerated by the reconnection electric field more times than are ions, which can explain the lower temperature ratios observed closer to the Earth.

How to cite: Chen, C. and Wang, C.-P.: Contribution of patchy reconnection to the ion to electron temperature ratio in the Earth’s magnetotail, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-83, https://doi.org/10.5194/egusphere-egu25-83, 2025.

X4.119

EGU25-8071

A new empirical model for Saturn’s radiation environment included in the TRAPPED framework

Angelica Sicard, Elias Roussos, Kostas Dialynas, Yixin Hao, Quentin Nenon, Aneesah Kamran, Piers Jiggens, and Fredrik Johansson

Missions are being studied to the systems of outer planets, including extended observation periods by local orbiters or possible landers, that require careful evaluation of the local radiation and plasma environment for design of both platform and science payload. Radiation impact potentially includes total cumulative doses, single event effects from short term enhancements and internal charging risk whilst plasma environments present risks of surface charging.
Under the ESA Project TRAPPED (Testbed for Radiation and Plasma Planetary Environments), a consortium comprising ONERA, IRAP, MPS and Academy of Athens has developed a flexible and easy-to-use environment model framework and related software for gas giant planet systems based on the wealth of data from visiting missions. Within this activity, derived specific models were developed for the Saturnian system.
Here, we will present the TRAPPED framework and more particularly the new specification model for Saturn’s radiation environment. This empirical model based on the last version of Cassini data (LEMMS, CHEMS and INCA) provides electron, proton and water-group ion fluxes in the magnetosphere of Saturn.

How to cite: Sicard, A., Roussos, E., Dialynas, K., Hao, Y., Nenon, Q., Kamran, A., Jiggens, P., and Johansson, F.: A new empirical model for Saturn’s radiation environment included in the TRAPPED framework, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8071, https://doi.org/10.5194/egusphere-egu25-8071, 2025.

X4.120

EGU25-12787

ECS

An empirical model for Saturn’s plasma environment within the TRAPPED framework

Aneesah Kamran, Quentin Nénon, Angélica Sicard, Yixin Hao, Elias Roussos, Kostas Dialynas, Piers Jiggens, Fredrik Johansson, and Fabrice Cipriani

As part of the ESA Testbed for Radiation and Plasma Planetary Environments (TRAPPED) project, we present the first empirical-based specification model of Saturn’s plasma environment based on the analysis of all publicly available plasma moment datasets derived using multiple techniques from Cassini observations made by the Cassini Plasma Spectrometer (CAPS) and the Radio and Plasma Wave Science (RPWS) instrument covering the entire 13-year mission.

We investigate the variability and spatio-temporal dynamics of the plasma moments with respect to various magnetic parameters including minimum normal distance to the current sheet, L-shell, latitude, and magnetic local time, and find the latter three parameters to be the most useful to organize the TRAPPED model plasma moments. The model moments include electron (cold and hot populations) and ion densities, temperatures and 3-dimensional ion velocities. We do not identify any clear variations with local time, despite previous Cassini-era studies indicating a local time variation related to an identified electric field in Saturn’s inner magnetosphere. Furthermore, our moment analysis results are consistent with seasonal and/or solar cycle modulation as reported in previous studies.

Despite the difference in the number of available observations between the Cassini mission and the Voyager 1 and 2 flybys, comparison of the TRAPPED model moments with moments derived from Voyager Plasma Science Experiment (PLS) observations are in relatively good agreement, which would suggest that there is no significant secular variation in Saturn’s magnetosphere, also consistent with previous Cassini-era studies.

Given that ambient magnetospheric plasma in planetary systems can induce spacecraft surface charging, it is imperative to develop a thorough understanding of planetary plasma environments to prepare for future space missions. ESA have recently highlighted Enceladus as a ‘top target’ for a future large-class mission, and thus this model will be used to support the planning and development of a future space mission to the Saturnian system.

How to cite: Kamran, A., Nénon, Q., Sicard, A., Hao, Y., Roussos, E., Dialynas, K., Jiggens, P., Johansson, F., and Cipriani, F.: An empirical model for Saturn’s plasma environment within the TRAPPED framework, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12787, https://doi.org/10.5194/egusphere-egu25-12787, 2025.