Magnetic field observations have a long history of advancing our understanding of ionospheric current flow, even before we launched space missions. Earlier magnetic field missions were single satellites that provided new insights into ionospheric current flow. Swarm is the first constellation focused on measuring magnetic fields from LEO. In this talk, we will focus on the value of knowing the magnetic field variation and discuss challenges, advances, and future opportunities.

One scientist's signal is another scientist's noise, and therefore working with magnetic perturbation leads to the collaboration of scientists from solid Earth to the magnetosphere. Opportunities can be challenges since magnetic observations include the signal from many sources which can be from far away or close by, making the interpretation of magnetic signals often difficult. In ionosphere-thermosphere numerical modeling, magnetic perturbations are not a standard diagnostic even though a wealth of data exists. While ionospheric data is used for data assimilation, magnetic data so far is not. A huge advantage of the Swarm satellite configuration is that it can unambiguously identify ionospheric current flow when the satellites are close. A similar concept is used by NASA Electrojet Zeeman Imaging Explorer (EZIE), a CubeSat mission scheduled for launch in spring 2025. In addition, EZIE is unique as it will measure the magnetic field around 80 km remotely via Zeeman splitting, to shed light on the substorm current flow and the equatorial electrojet.

In this presentation, we will describe the value of studying the ionospheric current to gain insights into the ionosphere-thermosphere system. We will show examples from high to low latitudes illustrating how magnetic perturbation especially in constellations and combined ground and space based data can advance our understanding of the MIT system. We conclude with thoughts about future observations.

How to cite: Maute, A., Yee, J.-H., Gjerloev, J., Alken, P., and Merkin, S.: Missions and efforts using magnetic field observations to advance our knowledge of the coupled magnetosphere-ionosphere-thermosphere (MIT) system, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6857, https://doi.org/10.5194/egusphere-egu25-6857, 2025.

In this study, we analyze electron density measurements from the Low-Earth Orbiting (LEO) satellite constellations Swarm and GRACE-FO to examine the effects of the May-2024 geomagnetic storm on the equatorial and low-latitude ionosphere. Results show that the equatorial ionization anomaly (EIA) was particularly enhanced on the dayside and depleted on the nightside. Notably, an intensification of the EIA was observed during early morning hours (at ~05/07 LTs) by the GRACE-FO and Swarm A satellites. The observed EIA modifications can be attributed to the strong influence of the electric fields and thermospheric winds. Comparisons with CHAMP and GRACE observations during the Halloween storm indicate an increase of a similar order of magnitude in the EIA’s crest-to-trough ratio (CTR) and L-value around similar local times and longitudes, emphasizing the May-2024 storm as one of the strongest geomagnetic storms in the space age. Additionally, strong equatorial plasma depletion (EPD) activity was noted, including EPDs detected during early morning hours at ~05 LT (~07 LT) by GRACE-FO (Swarm A). These EPDs reached very high apex altitudes of ~5000 km during pre-midnight and ~3400 km at early morning hours during 11-12 May, in contrast to ~1000 km during pre-storm conditions. The lower apex altitude of the early morning EPDs than of the pre-midnight EPDs suggests that these EPDs are generated after midnight and they are not remnants from the previous evening. This suggestion is also supported by ground-based ionosonde observations in Southeast Asia, combined with satellite data, which reveal an elevation of the ionosphere after midnight, supporting the Rayleigh-Taylor instability mechanism crucial for the EPD growth.

How to cite: Das, S. K., Stolle, C., Yamazaki, Y., Rodríguez-Zuluaga, J., Wan, X., Kervalishvili, G., Rauberg, J., Zhong, J., and Perwitasari, S.: On the low-latitude ionospheric responses to the May-2024 geomagnetic storm observed by LEO satellites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3337, https://doi.org/10.5194/egusphere-egu25-3337, 2025.

Geomagnetic storms significantly impact the morphology and dynamics of the Equatorial Ionization Anomaly (EIA). The geomagnetic storm of May 10, 2024, also known as the “Mother’s Day Storm”, was the most intense geomagnetic storm in the last two solar cycles. Given its severity, understanding the storm's impact on the ionosphere is crucial. This study investigates the variations of the low-latitude ionosphere during the Mother's Day Storm, utilizing observations from ESA’s Swarm satellites, as well as total electron density (TEC) estimates from the ground.

Data from the Langmuir Probes, the Electric Field Instrument (EFI), and TEC derived from GPS receivers onboard The Swarm satellites were used to analyze the F-region ionosphere. Additionally, ground-based TEC maps from the Madrigal database were employed to examine the altitudinal evolution of the EIA structure.

Results demonstrate a significant enhancement of the double-peak electron density structure of the EIA during the main phase of the storm (starting around 17 UT on May 10), with evidence of the super fountain effect. The EIA crests reached altitudes above the Swarm B satellite orbit (510 km), extending to approximately 40 degrees north and south of the equator. In contrast, the generation of the EIA was suppressed during the storm's recovery phase. These behaviors are interpreted in the context of storm-induced electric fields.

How to cite: Mohandesi, A., Knudsen, D. J., Skone, S., and Ghadjari, H.: Investigating Low-latitude Ionospheric Variations During the 2024 "Mother's Day Storm": Combined Swarm and Ground-Based Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14373, https://doi.org/10.5194/egusphere-egu25-14373, 2025.

The response of the ionosphere-thermosphere system in Europe during the severe geomagnetic storm of May 2024 was investigated. Between May 7 and 11, multiple X-class solar flares and at least five Earth-directed coronal mass ejections (CMEs) were observed. The initial CME impacted Earth at 12:30 PM UTC on May 10, triggering a geomagnetic enhancement and inducing a negative ionospheric storm over mid-latitude European stations, leading to data gaps on May 11 due to the "G condition" (wherein the electron density at the F2 layer maximum equals or falls below that of the F1 layer maximum).

Thermospheric parameters analyzed using the THERION method revealed a 60% increase in neutral [O] density at 300 km altitude and elevated thermospheric temperatures(~50% increase), while column [O] concentrations showed a ~30% decrease. Enhanced equatorward winds, peaking at 79 m/s, were observed between May 10 and 13. Comparative analysis with other longitudinal sectors confirmed significant regional responses, emphasizing the dynamic behavior of the coupled ionosphere-thermosphere system during severe geomagnetic events.

How to cite: Perrone, L., Mikhaylov, A., Sabbagh, D., and Bagiacchi, P.: Ionosphere-Thermosphere System Response During the May 2024 Geomagnetic Storm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4988, https://doi.org/10.5194/egusphere-egu25-4988, 2025.

A peculiar compressional Pc3 magnetic pulsation was observed by the Swarm satellites on the dayside which may have been caused by the Lamb wave generated at the Tonga undersea volcanic eruption on January 15, 2022. The difference between this and other usual compressional Pc3 pulsations observed at low and mid-latitudes is its spectral structure. The power spectral density (PSD) usually peaks at the periods between 20 and 30 sec, but in this event observed on the dayside orbit around the time when the Lamb wave passed under the Swarm orbit, the PSD peaks below 20 sec and is small in the periods longer than 20 sec. It is shown that this is a very rare case, although not the only one, during the period examined, i.e., from December 2013 to April 2022. The PSD has many sharp spectral peaks, but they don't have usual harmonic structure, and the frequencies of the peaks are nearly common with those of other similar events. The Pc3s observed at low-latitude (L<3 Re) ground magnetic stations simultaneously with the satellites show a very good correspondence of PSD peaks with those of the Swarm satellites although those of high-latitude station do not. The solar wind on January 15, 2022 was disturbed and high speed, so the possibility that the solar wind was the cause of the Pc3 cannot be completely excluded. However, the coincidence of the Pc3 appearance with the Lamb wave arrival, its peculiar spectral structure, and a comparison with ground magnetic observations suggest that this phenomenon is likely to be related to the Lamb wave arrival. A plasmaspheric cavity resonance excited by a magneto-sonic wave injected from the ionosphere via ionospheric dynamo could be a possible mechanism. This is probably the first report on a Pc3 magnetic pulsation possibly caused by lower atmospheric disturbance.

How to cite: Iyemori, T., Yokoyama, Y., and Aoyama, T.: A Pc3 magnetic pulsation possibly associated with the Lamb wave generated by the 2022 Tonga undersea volcanic eruption, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7665, https://doi.org/10.5194/egusphere-egu25-7665, 2025.

The Swarm data base is well-suited to address a number of topics of serious interest in space weather science and monitoring as for instance: spatial and temporal characteristics of ionospheric electron density, improving topside approaches in ionospheric models for monitoring and forecasting the dynamics of the geo-plasma environment. In this study, we developed a neural network-based electron density model using the electron density measured by Langmuir probes on the Swarm A and C satellites. Data from the years 2014 till 2021 has been used for this study, where the satellites have an approximate altitude range of 470-430 km. The model’s capability of showing large and small-scale features of the ionosphere was tested and the results show that the model is capable of showing the crest formations on both sides of the magnetic equator, as well as seasonal and diurnal variations. Furthermore, using the neural network-based model predictions, the nighttime winter anomaly (NWA) feature was investigated. The NWA is a small-scale feature that can be observed during low solar activity conditions at nighttime in the Northern Hemisphere at the American sector and in the Southern Hemisphere at the Asian sector. Such electron density models at specific height region can be used for three-dimensional ionosphere model validation as well as for the development of improved ionosphere models. Again, accurate modelling and monitoring of ionospheric electron density at certain height region can help prediction of space weather impact.

How to cite: Adolfs, M. and Hoque, M. M.: Electron density modelling at Swarm height using Neural Networks for space weather monitoring, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13355, https://doi.org/10.5194/egusphere-egu25-13355, 2025.

An intense surge in equatorial electron temperature (T_e) at sunrise, known as the morning T_e overshoot, has been one of the most widely studied ionospheric features since its discovery in the early Space Age. Despite extensive research, its behavior during geomagnetic storms remains poorly understood. Using global electron temperature observations by the CHAllenging Minisatellite Payload (CHAMP) mission in 2002-2010, we develop a neural network T_e model, which helped us uncover a two-stage response of the morning T_e overshoot to geomagnetic activity. During the storm’s main phase, electron temperatures in the overshoot region exhibit a pronounced enhancement, which is followed by a dramatic depletion exceeding 1000 K and the disappearance of the overshoot during the recovery phase. This two-phase evolution corresponds to the initial impact of a westward prompt penetration electric field (PPEF), which reduces electron densities therefore allowing for a more efficient energy exchange between the newly ionized particles at sunrise and lower energy (depleted) ambient plasma. The initial PPEF influence is overtaken by the eastward disturbance dynamo field later in the storm, which flips the ExB drift from downward to upward and lifts more electrons into the F-region. Increased electron densities enhance the cooling rates leading to the disappearance of the overshoot in the recovery phase of the storms. Our findings shed new light on the dynamics of the morning electron temperature overshoot and highlight the capability of digital twin models to uncover previously unrecognized physical phenomena in the near-Earth space environment. Additionally, we discuss the applications of the developed model for various ionospheric applications, including the calibration of electron temperatures from Swarm Langmuir Probes. 

How to cite: Smirnov, A., Shprits, Y., Lühr, H., Pignalberi, A., Kronberg, E., Prol, F., and Xiong, C.: Extreme two-phase change of the ionospheric electron temperature overshoot during geomagnetic storms uncovered by neural networks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19863, https://doi.org/10.5194/egusphere-egu25-19863, 2025.

Geomagnetic field and ionospheric environment monitoring is presently achieved with huge success by the three satellites of the Swarm Earth Explorer ESA constellation launched in November 2013. Maintaining and improving observations beyond the lifetime of Swarm is critical for both science investigations and advanced applications. NanoMagSat aims at fulfilling this goal. This much cheaper mission is currently in Phase B within the context of the ESA Scout program. It will deploy and operate a new Low-Earth orbiting constellation of three identical 16U nanosatellites, using two inclined (~ 60°) and one polar orbits at an initial altitude of 545 km, to complement and take over the Swarm mission. The mission is planned to start deploying end of 2027, for a minimum of three years of full constellation operation between 2028 and 2031.

This constellation is designed to cover all local times (LT) at all latitudes, with special emphasis on latitudes between 60°N and 60°S, where all LT will be visited within about a month, much faster than is currently achieved by the Swarm constellation. Each satellite will carry an advanced Miniaturized Absolute scalar and self-calibrated vector Magnetometer (MAM) with star trackers (STR) collocated on an ultra-stable optical bench at the tip of a deployable boom, a new compact High Frequency Magnetometer (HFM) (at mid-boom), a multi-Needle Langmuir Probe (m-NLP) and dual frequency GNSS receivers (all on the satellite body). This payload suite will acquire high-precision/resolution oriented absolute vector magnetic data at 1 Hz, very low noise scalar and vector magnetic field data at 2 kHz, electron density data at 2 kHz, and electron temperature data at 1 Hz. GNSS receivers will also allow top-side TEC and ionospheric radio-occultation profiles to be recovered.

In this presentation, the main science goals of the mission will first be introduced and the rationale for the choice of the payload and constellation design next explained. The various data products currently planned to be produced will also be described. Special emphasis will be put on the innovative aspects of the mission with respect to Swarm and other previous missions. Finally, the benefit of relying on such nanosatellite constellations for maintaining long-term observations of the magnetic field and ionospheric environment, to complement ground-based observations will also be discussed.

How to cite: Hulot, G., Coïsson, P., Léger, J.-M., Clausen, L. B. N., Jørgensen, J. L., van den Ijssel, J., Chauvet, L., Jager, T., Deconinck, F., Nieto, P., Cipriani, F., Pastena, M., and Lejault, J.-P.: The Upcoming ESA Scout NanoMagSat Mission, a Nanosatellite Constellation to Further Improve Geomagnetic Field and Ionospheric Environment Monitoring and Modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9287, https://doi.org/10.5194/egusphere-egu25-9287, 2025.

Modern geomagnetic field models can successfully represent many details of the observed large-scale field and its slow time changes. However, the obtained model uncertainty is often underestimated, which limits our ability to evaluate the reliability of signals recovered in the field models. The increasing amount of globally distributed, high-quality magnetic data observed by low-Earth orbit satellites, such as Swarm, MSS-1 and the planned NanoMagSat mission, present an opportunity to improve the model uncertainty by providing important statistical information on the expected errors of the input magnetic data used in field modelling.  

During the field model estimation, data errors are usually assumed to be uncorrelated in time and independent of position. However, limitations in the parameterization of the models regarding magnetospheric and ionospheric sources lead to residuals between model predictions and magnetic observations that are not only larger than the expected measurement noise but are also correlated and varying with position. Not adequately describing these correlations during the model estimation leads to unrealistic model uncertainties, which hinders, for example, their use in applications such as assimilation into numerical Geodynamo simulations.

Here, the statistics of vector residuals between magnetic observations from the Swarm satellites and the CHAOS-7 geomagnetic field model predictions are studied by computing sample means and covariances for the field components as a function of time and magnetic coordinates. This analysis reveals significant covariances, particularly at mid-to-high latitudes. The sample covariances are used to construct non-diagonal data error covariance matrices, which can be used in field modelling.

Finally, test field models built using the non-diagonal data error covariances matrices within the CHAOS modelling framework are discussed, illustrating the effect of correlated data errors on the recovered fields and the associated model uncertainties.

How to cite: Kloss, C.: Accounting for correlated errors in Swarm magnetic data within the CHAOS field modelling framework, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11188, https://doi.org/10.5194/egusphere-egu25-11188, 2025.

Measurements from geomagnetic satellites continue to underpin advances in geomagnetic field models that describe Earth’s internally generated magnetic field. Here we present a new field model: MSCM that integrates vector and scalar data from the Swarm, CSES, and MSS-1 satellites. The model spans 2014.0 to 2024.5, incorporating the core, lithospheric, and magnetospheric fields, showing similar characteristics to other published models. For the first time, we demonstrate that incorporating CSES vector data successfully produces a geomagnetic field model, albeit one in which the radial and azimuthal CSES vector components are Huber downweighted. We further show that data from MSS-1 can be used to construct a fully time-dependent geomagnetic field model. MSCM identifies new behaviour of the South Atlantic Anomaly, the broad region of low magnetic field intensity over the southern Atlantic. This prominent feature appears split into a western and eastern part, each with its own intensity minimum. Since 2015, the principal western minimum has undergone only modest intensity decreases of 290 nT and westward motion of 20km/yr, while the recently-formed eastern minimum has shown an intensity drop 2-3 times greater of 730nT with no apparent motion. 

How to cite: Gao, Y., Wang, Z., Livermore, P., Rogers, H., and Liu, C.: MSCM: A geomagnetic Model derived from Swarm, CSES and MSS-1 satellite data and the evolution of the South Atlantic Anomaly, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12183, https://doi.org/10.5194/egusphere-egu25-12183, 2025.