We compare solar wind interactions of the solar system's terrestrial planets. We focus on solar wind coupling with the (induced) magnetospheres of Mercury, Venus and Mars and compare their space weather processes to Earth. Our analysis is based on global ion-kinetic hybrid particle simulations with the open source RHybrid model platform and in situ particle and field observations on spacecraft exploration missions like BepiColombo. In the model, ions are treated as particles accelerated by the Lorentz force self-consistently coupled with the evolution of magnetic field via Maxwell's equation, while electrons form a charge-neutralizing fluid. We highlight differencies and similarities in ion dynamics and velocity distributions as well as magnetic ultra-low frequency waves excited in the foreshock and modulating planetary plasma environments.
How to cite: Jarvinen, R., Kallio, E., Honkonen, I., and Phillips, D.: Solar wind coupling with magnetospheres of terrestrial planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1380, https://doi.org/10.5194/egusphere-egu25-1380, 2025.
In May 2024, the most intense geomagnetic storm since 2003 was caused by coronal mass ejections from the Sun. It has triggered a surge of interest within the international space science community with dedicated workshops and planned special issues. Our study focuses on the ionosphere-thermosphere responses in the northern polar region based on multiple observations from the ground-based instruments (including the EISCAT incoherent scatter radar on Svalbard, GNSS TEC receivers, SuperMAG magnetometers, and SuperDARN coherent scatter radars) and satellites (including the Swarm, GRACE-FO, TIMED, and DMSP satellites). The EISCAT Svalbard radar, GNSS TEC, and satellite observations showed strong and large-scale ionospheric electron density depletion over the northern polar ionosphere. During the superstorm, strong solar wind energy input was dissipated at high latitudes. We apply a new method to estimate the integral Joule heating power using SuperDARN, SuperMAG and AMPERE data. The result showed the Joule heating power was up to 1300 GW. The strong heating increased the ion temperature as observed by the EISCAT Svalbard radar. The ion-chemistry-coupled EISCAT analysis showed how the transition altitude from molecular ions to O+ was increased from 200 km to 380 km during the main and recovery phases of the storm. The strong heating also induced an upwelling of the thermosphere in the polar region as evidenced by the strong increase in the neutral mass density observed from the Swarm and GRACE-FO satellites and the strong depletion of ΣO/N2 by GUVI onboard TIMED. The changes both in ion temperature and neutral composition affected the F-region recombination and caused a long lasting strong depletion up to 80 % in the electron density in the polar ionosphere on 11 May 2024.
How to cite: Cai, L., Aikio, A., Prasannakumara Pillai Geethakumari, G., Vanhamäki, H., Virtanen, I., Oyama, S., Zhang, Y., Zhang, J., and Hairston, M.: Polar Ionosphere-thermosphere coupling during the May 2024 geomagnetic superstorm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10465, https://doi.org/10.5194/egusphere-egu25-10465, 2025.
The strength of terrestrial magnetospheric convection and transpolar ionospheric flow is well predicted by the ‘reconnection electric field’ EKL [1], a function of the solar wind velocity, V, and the interplanetary magnetic field, B. The convection response is linear under low EKL, but appears to saturate at high EKL, and several physical mechanisms have been proposed to explain this effect (see [2] for review). However, others postulate that the error distribution of EKL measurements introduces a regression bias that could account for the apparent saturation [3,4,5]. For space weather applications, EKL is typically measured near the L1 Sun-Earth Lagrange point, so we are motivated to quantify the distribution of errors introduced in propagating such measurements (i) from L1 to a region just outside the Bow Shock and (ii) onward to the polar ionosphere.
To characterise the error distribution in step (i), we compared OMNI solar wind measurements near L1[6], time-shifted to a model Bow Shock nose location, with a new 22-year database of periods for which the ESA Cluster satellites were just inside the pristine solar wind (over 5000 hours in total). We find that replacing OMNI-projected EKL measurements with direct Cluster measurements has only marginal effect on the ionospheric response as measured by, e.g., the cross-polar cap potential [7] or the PCC Polar Cap index [8] which remain non-linear. We discuss the implication of this result together with a further consideration of errors introduced between Cluster (near the Bow Shock) and the polar ionosphere.
References
1. Kan, J. R., and L. C. Lee (1979) https://doi.org/10.1029/GL006i007p00577
2. Borovsky, J. E. et al. (2009) https://doi.org/10.1029/2009ja014058
3. Borovsky, J. E. (2022) https://doi.org/10.3389/fspas.2022.867282
4. Di Matteo, S. and N. Sivadas (2022) https://doi.org/10.3389/fspas.2022.1060072
5. Sivadas, N., and D. G. Sibeck (2022) https://doi.org/10.3389/fspas.2022.924976
6. Papitashvili, N. E. (2024) https://omniweb.gsfc.nasa.gov
7. Shepherd, S. G et al. (2002) https://doi.org/10.1029/2001JA000152
8. Stauning, P. (2021) https://doi.org/10.1051/swsc/2020074
How to cite: Rogers, N., Wild, J., and Grocott, A.: Quantifying uncertainty in the solar wind drivers of magnetospheric convection using OMNI and Cluster measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3207, https://doi.org/10.5194/egusphere-egu25-3207, 2025.
How to cite: Sivadas, N., Walach, M.-T., and Sibeck, D.: Uncertainty in L1 Measurements and its Effect on Geomagnetic Response, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14063, https://doi.org/10.5194/egusphere-egu25-14063, 2025.
How to cite: Katrougkalou, M. C., Kullen, A., Cai, L., Roth, L., and Zhang, Y.: HiLDAs, cusp aurora and their connection to transpolar arcs: Classification, Conjugacy and Origins, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17540, https://doi.org/10.5194/egusphere-egu25-17540, 2025.
Solar wind - magnetosphere coupling is a core element of space weather and magnetospheric physics. While it is generally understood that this coupling process is complex and involves effects from both the upstream (magnetosheath) and downstream (magnetosphere) plasma conditions, nearly all empirical models of solar wind - magnetosphere coupling assume this process is one-way. That is to say, coupling functions predict the energy transport or open magnetic flux change at the magnetopause as dependent only on the upstream solar wind conditions. In this work we test the simplifying hypothesis that solar wind - magnetosphere coupling is one-way by using a numerical experiment. The Space Weather Modeling Framework (SWMF) is used in the Geospace configuration to simulate Earth's magnetosphere under steady solar wind input conditions with typical driving solar wind inputs and dipole tilt. A 48 - hour test is simulated with the IMF conditions changing every two hours. This test is repeated with constant plasma conditions 9 times, for a total of 216 steady state solar wind conditions. The MHD output data is used to identify the magnetopause and calculate energy flux through the open magnetopause as a direct measure of solar wind - magnetsophere coupling. It is found that while the empirical coupling functions predict trends in the average energy flux through the magnetopause, there is significant variability as measured by the total variation. The results of this numerical experiment refute the one-way coupling hypothesis and highlight the need for an empirical coupling function which includes magnetosphere effects.
How to cite: Brenner, A., Pulkkinen, T., and Liemohn, M.: Revealing Magnetosphere Feedback on Solar Wind - Magnetosphere Coupling via Numerical Experiment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12343, https://doi.org/10.5194/egusphere-egu25-12343, 2025.
The coupling between the mid-magnetotail and the high-latitude ionosphere is driven by dynamic processes such as earthward bursty bulk flows (BBFs), which facilitate plasma transport to the inner magnetosphere. These flows interact with the ionosphere through Field-Aligned Current (FAC) systems. This work investigates the relationship between BBFs and FACs by utilizing nearly a decade of ionospheric measurements from the Swarm constellation, complemented by data from magnetospheric missions, particularly the Magnetospheric Multiscale (MMS) Mission. Approximately 2000 BBFs detected during the MMS tail seasons from 2017 to 2021 were mapped onto the ionosphere using Tsyganenko models. The mapping revealed a statistically consistent pattern of BBF footpoints between 65° and 75° magnetic latitude and 20 to 04 hour MLT, with a peak in the pre-midnight sector. To examine the connection between BBFs and ionospheric currents, we compared these footpoint locations with statistical maps of Swarm-derived FACs during BBF and non-BBF periods. We further analysed whether BBF periods correspond to significant changes in FACs. This approach aims to uncover the relationship between BBF mapping points and FAC dynamics, providing insights into the magnetosphere-ionosphere coupling processes.
How to cite: Lanabere, V., Dimmock, A., Buchert, S., Marghitu, O., Richard, L., and Khotyaintsev, Y.: A Statistical Study of Field-Aligned Currents During BBF and Non-BBF Periods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8236, https://doi.org/10.5194/egusphere-egu25-8236, 2025.
Ultralow frequency (ULF, ~2mHz-5Hz) magnetohydrodynamic waves are ubiquitous in Earth's magnetosphere and are driven by a range of mechanisms with energy sources both internal and external to it. ULF waves are an important coupling mechanism between the solar wind, magnetosphere, and ionosphere. ULF waves in the Pc5 band (~1.7-6.7mHz) play significant roles in the solar-terrestrial energy pathway as well as in radiation belt dynamics, namely the radial diffusion of energetic electron populations.
The coherent-scatter radars in the SuperDARN network are ideal for the study of ULF waves. In radar backscatter, ULF waves are identified as periodic oscillations in the line-of-sight Doppler velocities of field-aligned plasma irregularities in the upper-ionosphere. These oscillations are explained as ExB drift fluctuations induced by the waves' electric field component. SuperDARN radars offer wide and fixed fields-of-view, a relatively fine spatial resolution compared to ground magnetometers, and a 60s temporal resolution, thus facilitating the observation of Pc5 waves with a wide range of scale sizes as well as of their propagation characteristics.
Here we present statistical work on the occurrence of Pc5 waves observed in the common mode backscatter recorded by the Hankasalmi SuperDARN radar throughout the years 2013-14 as well as that of their spatio-temporal characteristics. Over 200 discrete wave events are included. The distribution of and the relationships between a number of their propagation, spectral, and spatial characteristics are considered, as well as their relationships to solar wind drivers.
How to cite: Rennie, S., Milan, S., and Imber, S.: Studying the Occurrence of Pc5 ULF waves and their Spatio-temporal Characteristics Using SuperDARN, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12228, https://doi.org/10.5194/egusphere-egu25-12228, 2025.
A key component of solar wind-magnetosphere-ionosphere coupling manifests in the high-latitude field-aligned currents and the spatial extent of open magnetic flux in the polar cap. This in turn drives changes in the cross-polar cap potential (CPCP), like saturation under extreme conditions, and dynamics in the ionospheric electric field, like over- or under-shielding at sub-auroral latitudes. While there have been many studies linking solar wind and interplanetary magnetic field (IMF) driving conditions with the change in the polar cap area, interhemispheric differences have been less well explored. To mitigate uncertainties in connecting the driving conditions to high-latitude field-aligned current characteristics, a criteria of extended, quasi-steady IMF intervals are used for a statistical survey of the AMPERE current density distributions from January 2010 through May 2022. Fits to these distributions following Clausen et al. (2012) are applied in both hemispheres, and then used to derive the area enclosed poleward of the R1 currents. We present an overview of the statistical results of the northern and southern hemisphere current densities, the resulting polar cap areas, and an initial assessment of the CPCP for a given conductance profile. In general, AMPERE observations reveal larger polar cap areas occurring slightly more frequently in the southern hemisphere. Examining the dependencies of the polar cap areas on upstream conditions, there is a clear dependence on IMF BZ seen for both hemispheres, as expected. However, there is a notable interhemispheric asymmetry in the distribution of polar cap areas as a function of IMF clock angle, specifically for clock angles of 90° versus 270°. Along with the contribution to interhemispheric asymmetries arising from the geomagnetic pole location, these results point to the importance of the dayside conductivity gradient in the closure of the high-latitude field-aligned currents under varying upstream driving conditions.
How to cite: Vines, S., Mo, W., Anderson, B., Allen, R., Coxon, J., Maute, A., and Knipp, D.: Impacts of Solar Wind Driving on Interhemispheric Asymmetries in the Polar Cap, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6855, https://doi.org/10.5194/egusphere-egu25-6855, 2025.
Posters on site: Mon, 28 Apr, 10:45–12:30 | Hall X4
Auroral currents are important manifestations of solar wind-magnetosphere interaction, which is strongly controlled by the direction of the interplanetary magnetic field (IMF). While the dawn-dusk (By) component of the IMF is known to play an important role in this interaction, its effects on geomagnetic activity are usually assumed to be independent of its sign. However, several recent studies have shown evidence that especially the westward auroral electrojet is significantly stronger for By > 0 (By < 0) in Northern Hemisphere winter (summer). The physical mechanism of the By effect is still not fully understood, but significant progress has been achieved in recent years. Here we review how IMF By modulates auroral electrojets, field-aligned currents and ionospheric particle precipitation. These results are based on various datasets, including geomagnetic indices, AMPERE, POES and DMSP satellites. Our results highlight the importance of the IMF By component for space weather and must be taken into account in the future space weather modeling.
How to cite: Holappa, L., Laitinen, J., and Vanhamäki, H.: IMF By dependence of ionospheric currents and particle precipitation during non-zero dipole tilt, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18217, https://doi.org/10.5194/egusphere-egu25-18217, 2025.
We statistically investigate convective earthward fast flows (V⊥ > 200 km/s) using data measured by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission in the tail plasma sheet during 2011-2022. Statistical results show that under the penetration and induction of the dusk-dawn interplanetary magnetic field component (IMF By), the magnetotail By aligned with the direction of IMF By on average dominates the entire investigated near-lunar tail plasma sheet region, regardless of the hemisphere. Compared with the statistical results of the near-Earth magnetotail, IMF By has a greater impact on the near-lunar magnetotail (the span of influence is greater). The influence of IMF By on magnetotail By may have a dusk-dawn asymmetry characteristic, with a weaker influence in the premidnight compared to the postmidnight. In addition, we find that the impact of IMF By on earthward perpendicular fast flows exhibits interhemispheric asymmetry in average V⊥y and it is highly correlated with the direction of magnetotail By. In more than 80% of the data bins, both tail By and V⊥y are in their dominating directions. In those bins where the V⊥y direction is opposite to the dominating direction, only slightly more than 50% of the bins have tail By in the direction opposite to the dominating tail By. Based on the statistical results, we infer that nonzero IMF By conditions affect the magnetotail and fast earthward convection at lunar distances. However, occasionally local dynamics can have a significant impact on magnetotail By and V⊥y, even overriding the influence of IMF By, which has been observed before at near-Earth distances.
How to cite: Pitkänen, T., Liu, T., Nilsson, S., Kullen, A., Park, J.-S., Hamrin, M., Shang, W., Wang, H., and Yao, S.: IMF By influence on fast earthward convection flows in the near-lunar magnetotail, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5338, https://doi.org/10.5194/egusphere-egu25-5338, 2025.
Magnetospheric ultra-low frequency (ULF) waves are driven by multiple sources. In this study we focus on two sources: interplanetary (IP) shocks that are large-scale events and foreshock transients that are mesoscale events. The abrupt variations of interplanetary magnetic field (IMF) and solar wind parameters in IP shocks are known to generate Pc5 range (2-7 mHz) ULF waves in the magnetosphere. The impact angle – the angle between the Sun-Earth line and IP shock normal vector – has been observed to affect the generation of magnetospheric ULF waves. Discontinuities in the IMF can create transient phenomena in Earth's foreshock. The largest transient phenomena, foreshock bubbles and hot flow anomalies, have a core with low density and magnetic field strength and a boundary with enhanced density and field strength. These changes in the density can cause outward and inward motions of the magnetopause and thus generate Pc5 ULF waves in the magnetosphere. To get novel insights on how the ULF waves are distributed inside the magnetosphere, we use a new ground-based, 1-minute resolution, magnetic local time dependent Pc5 ULF index derived from SuperMAG data. We study the local time dependence of magnetospheric ULF waves generated by IP shocks and foreshock transients and whether this dependence is related to the impact angle of IP shocks and impact point of foreshock transients. In addition, this study assesses the suitability of the new index for studying the ULF wave activity driven by foreshock transients.
How to cite: Lipsanen, V., Turc, L., Hoilijoki, S., Ojuva, M., Tao, S., Dahani, S., and Kilpua, E.: Local time dependence of ULF wave activity driven by interplanetary shocks and foreshock transients, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10674, https://doi.org/10.5194/egusphere-egu25-10674, 2025.
Solar wind drives magnetospheric dynamics through coupling with the geospace system at the magnetopause. While upstream fluctuations correlate with geomagnetic activity, their impact on the magnetopause energy transfer is an open question. We examine three-dimensional global simulations using the Geospace configuration of the Space Weather Modeling Framework to study the effects of solar wind fluctuations during a substorm event. We demonstrate that upstream fluctuations intensify the energy exchange at the magnetopause increasing both energy flux into and out of the system. The increased energy input is reflected in ground indices. The fluctuations also regulate the energy transport within the magnetotail neutral sheet. We complement our numerical efforts by using a large statistical set of over 4,000 magnetopause crossings of the Magnetospheric Multiscale mission to resolve the local energy exchange at the low-latitude dayside magnetopause. We aim at revealing how the interplay between the current state of the system and external drivers reflects to the boundary dynamics. As the exchanged energy fundamentally determines how the solar wind drives magnetospheric activity, it is important to understand where and under which local and global conditions the most significant energy transfer rates occurs.
How to cite: Ala-Lahti, M., Pulkkinen, T., Brenner, A., Tribu, N., Keebler, T., and Kilpua, E.: Quantifying the Importance of Upstream Magnetic Field Fluctuations for Solar Wind-Magnetosphere Coupling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11739, https://doi.org/10.5194/egusphere-egu25-11739, 2025.
Transient changes in solar wind dynamic pressure, such as positive and negative pressure pulses, can lead to magnetospheric compression or expansion and the formation of global current systems. These current systems, in turn, generate electric fields in the ionosphere, which can propagate to low geomagnetic latitudes. While the effects of positive pressure pulses have been studied relatively extensively, negative pressure pulses are less studied and understood. For this study, we examine in detail the negative pressure pulse event that occurred during the main phase of the recent geomagnetic storm on 22-23 March 2023 with Dstmin = -163 nT. For this event, a strong negative pressure pulse during the main phase imposed significant perturbations to the coupled ionosphere-magnetosphere system, as evidenced by observations from Swarm, AMPERE, and ground-based magnetometers. We use a global 3D MHD model SWMF BATS-R-US coupled to the ionospheric solver to track the chain of effects from solar wind drivers to the ionosphere, interpret multi-s/c observations, and understand the coupling mechanisms. The MMS mission was in the solar wind near the bow shock, which allowed the use of MMS data for the timing analysis. Based on model results and analysis of observations, we relate changes in solar wind drivers to changes in field-aligned currents observed by Swarm and AMPERE. We show that the pressure pulse is related to the formation of an additional pair of field-aligned currents at low geomagnetic latitudes, which creates the overshielding electric field. We relate the overshielding field to the dynamics of Region II currents in both observations and the model and discuss the role of the ring current in this process.
How to cite: Buzulukova, N., Le, G., Liu, G., and Wu, C.-C.: Magnetosphere-Ionosphere Coupling During Negative Pressure Pulse and Formation of Ionospheric Overshielding Electric Field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14617, https://doi.org/10.5194/egusphere-egu25-14617, 2025.
It is well-known that the dayside tip of a transpolar arc (TPAs) typically merges with the auroral cusp. Studying the location of the auroral cusp during TPA events allows us to better understand how the evolution of transpolar arcs is coupled to processes along the dayside magnetopause.
This work is based on 12 months DMSP SSUSI images. Only those images are taken into account, where near-simultaneous SSUSI images exist from both hemispheres. We identified several tens of cases where the auroral cusp is clearly visible while multiple TPAs appear simultaneously in at least one hemisphere. The results show that the cusp location during TPAs depends clearly on the interplanetary magnetic field (IMF) Bx and By components, and that the effect on the cusp location is opposite in the two hemispheres. While the longitudinal dependence is expected from previous studies, our statistical results show also a clear latitudinal dependence on IMF Bx and By. The best correlation with IMF Bx and By is found for summer hemisphere events.
Superposed epoch analysis plots show that in average, the auroral cusp becomes visible after IMF Bz drops from strongly to weakly northward IMF. Mapping the auroral cusp location to the magnetopause with help of the T96 magnetospheric model for different IMF inputs confirms what could be expected: the auroral cusp brightening appears after the magnetospheric cusp has moved from high to lower latitudes. Mapping results for different time shifts between IMF input and auroral signatures indicate a 15 min time delay between IMF and auroral cusp occurrence, which is in agreement with previous reports.
How to cite: Kullen, A., Holmen, C., Thor, S., Katrougkalou, M., Cai, L., and Zhang, Y.: IMF control of cusp aurora location during multiple transpolar arcs, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19241, https://doi.org/10.5194/egusphere-egu25-19241, 2025.
The interaction between the solar wind and Earth’s magnetosphere can induce significant changes in the magnetosphere-ionosphere (M-I) system. This study explores the M-I responses to a negative solar wind pressure pulse event on 23 March 2024. The event was marked by a sharp solar wind dynamic pressure drop of ~10 nPa, which preceded the onset of G2 and G4-class geomagnetic storms on 23 and 24 March 2024. The negative pressure pulse occurred at 14:06 UT, as confirmed by THEMIS satellite observations.
Using Global Navigation Satellite System (GNSS)-Total Electron Content (TEC), ground magnetometer data, and AMPERE observations, the study examined the impacts of the pressure pulse on the coupled M-I system. Observations revealed a pronounced reduction in TEC at high latitudes, particularly in the European afternoon sector, following the pressure drop. This significant perturbation in electron density is postulated to result from the magnetospheric expansion during the negative pressure pulse. The H-component of Earth’s magnetic field exhibited a marked global decrease across all longitude sectors following the pressure drop, attributed to ground perturbations caused by reduced magnetopause currents and weakened magnetospheric fields. AMPERE observations further revealed a reduction in field-aligned current density, corroborating the observed ionospheric and geomagnetic responses.
This study delineates the pressure drop-induced effects from storm-related electrodynamic and neutral dynamic variations by isolating the distinct timing of the pressure pulse event, characterized by steady IMF conditions prior to the onset of the geomagnetic storm. The findings underscore the critical role of negative solar wind pressure pulses as standalone drivers capable of triggering rapid and widespread changes in the M-I system.
How to cite: Kakoti, G., Shiokawa, K., Otsuka, Y., Shinbori, A., Nishioka, M., and Perwitasari, S.: Exploring Magnetosphere-Ionosphere Responses to Negative Solar Wind Pressure Pulses: Case Study of 23 March 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7987, https://doi.org/10.5194/egusphere-egu25-7987, 2025.
Between 23 and 25 May 2002 the solar wind, due to very low plasma density, became sub‐ Alfvénic for enough time to promote the establishment of Alfvén wings that can limit typical solar wind‐ magnetosphere coupling. During this interval, the interplanetary magnetic field (IMF) was oriented northward and duskward, with a slightly dominant BY component; driving of the magnetosphere was expected to be low. Many signatures are used to assess solar wind‐magnetosphere‐ionosphere coupling, including ultraviolet (UV) observations of the auroral zone to infer monoenergetic electron precipitation and radio observations of auroral kilometric radiation (AKR) to infer the development of the auroral acceleration region. Observing these signatures with the IMAGE (Imager for Magnetopause‐to‐Aurora Global Exploration) and Wind spacecraft, we find evidence of auroral acceleration that allowed amplification of AKR to similar intensities as during super‐ Alfvénic coupling. This coincides with polar electron aurora around 8° square in latitude and at magnetic latitudes greater than 88°. The multipoint radio observations imply sources are generated along a constrained flux tube. Given the primary coincidence of AKR and the electron polar spot ∼3 hr following the incidence of minimally sub‐Alfvénic (MA ∼ 0.4) solar wind at Earth, this acceleration occurs while the Alfvén wings are most complete. Given the IMF conditions, auroral morphology of the polar spot and the inference of an upward field‐aligned current, the magnetospheric dynamics are most related to those of the high‐latitude dayside aurora (HiLDA). These observations are the first to show AKR amplification from HiLDA and during a sub‐Alfvénic magnetosphere, highlighting the possibility of strong localized coupling under quiet geomagnetic conditions.
How to cite: Waters, J. E., Lamy, L., Milan, S., Walach, M.-T., and Chané, E.: Auroral Acceleration at the Northern Magnetic Pole During Sub‐Alfvénic Solar Wind Flow at Earth, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20287, https://doi.org/10.5194/egusphere-egu25-20287, 2025.
Posters virtual: Thu, 1 May, 14:00–15:45 | vPoster spot 3
EGU25-12754 | Posters virtual | VPS27 | Highlight
Global Geomagnetic Response and Impact During the 10 May 2024 Gannon Storm – Observations and ModelingThu, 01 May, 14:00–15:45 (CEST) | vP3.17
Space weather causes geomagnetic disturbances that can affect critical infrastructure. Understanding the dynamic response of the coupled solar wind-magnetosphere-ionosphere system to severe space weather is essential for mitigation purposes. This paper reports on a detailed analysis of the most recently observed May 10, 2024, storm. We demonstrate that the global response to the storm dynamics was strikingly different in various sectors and at various latitudes. Results in the American and European sectors show that the most extreme mid-latitude response was associated to substorm related activity. However, no adverse impact of the storm on bulk power systems was report in North America or other parts of the world.
How to cite: Ngwira, C. and Weygand, J.: Global Geomagnetic Response and Impact During the 10 May 2024 Gannon Storm – Observations and Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12754, https://doi.org/10.5194/egusphere-egu25-12754, 2025.
