Thermospheric effects during the magnetic superstorms in May 2024 and October-November 2003 in the Northern Hemisphere and the ionospheric response to them

We study the spatiotemporal variations of ionospheric parameters over the regions of Eurasia by analyzing data from chains of high- and mid-latitude ionosondes during the extreme magnetic storm in May 2024. The analysis of ionospheric parameters allowed us to note strong latitudinal and longitudinal differences in variations of the analyzed parameters under quiet conditions before the onset of the magnetic storm and during its development. Almost immediately after the onset of the storm at 17:00 UT on May 10, 2024, according to data from all ionosondes, a sharp drop in the electron density at the height of the F2-layer maximum was recorded, regardless of the local time at the measurement point. Ionosondes of the high-latitude chain showed a complete absence of data (radio signal blackout) during the main and early recovery phases of the storm until the evening of May 12, 2024, i.e. more than one and a half days. Additional bursts of geomagnetic activity during the recovery phase of the storm were also accompanied by significant and prolonged decreases in the electron density according to ionosonde measurements at all longitudes of Eurasia. The recovery of ionospheric ionization began on May 14–15 at all longitudes of the mid- and high-latitude regions of Eurasia. A long-term negative disturbance of electron density covering a huge territory of mid-latitude Eurasia was caused by an extraordinary, catastrophic drop in the [O]/[N2] ratio according to satellite measurements of GUVI TIMED during the superstorm for almost three days. The response of the thermospheric composition of neutral gas to the processes developing at high latitudes of the Northern Hemisphere on May 10–15, 2024 was global, with penetration of the thermospheric disturbance at almost all longitudes up to the equatorial latitudes (~10° N) and with very low values of the [O]/[N2] ratio ~0.1÷0.4. Significant differences in the spatiotemporal variations of the thermospheric composition of neutral gas were revealed during the most extreme geomagnetic storms of the current 21st century — in May 2024 and October–November 2003 (Halloween storms). The magnetic superstorm in May 2024 was much more geoeffective than the superstorms in October–November 2003, and caused a significantly different ionospheric response at different longitudes and latitudes of the Northern Hemisphere.

This study investigates the ionospheric response over China during the geomagnetic storm that occurred on 1–2 December 2023. The data used include GPS measurements from the Crustal Movement Observation Network of China, BDS-GEO satellite data from IGS MEGX stations, [O]/[N2] ratio information obtained by the TIMED/GUVI, and electron density (Ne) observations from Swarm satellites. The Prophet time series forecasting model is employed to detect ionospheric anomalies. VTEC variations reveal significant daytime increases in GNSS stations such as GAMG, URUM, and CMUM after the onset of the geomagnetic storm on 1 December, indicating a dayside positive ionospheric response primarily driven by prompt penetration electric fields (PPEF). In contrast, the stations JFNG and CKSV show negative responses, reflecting regional differences. The [O]/[N2] ratio increased significantly in the southern region between 25°N and 40°N, suggesting that atmospheric gravity waves (AGWs) induced thermospheric compositional changes, which played a crucial role in the ionospheric disturbances. Ne observations from Swarm A and C satellites further confirmed that the intense ionospheric perturbations were consistent with changes in VTEC and [O]/[N2], indicating the medium-scale traveling ionospheric disturbance was driven by atmospheric gravity waves. Precise point positioning (PPP) analysis reveals that ionospheric variations during the geomagnetic storm significantly impact GNSS positioning precision, with various effects across different stations. Station GAMG experienced disturbances in the U direction (vertical positioning error) at the onset of the storm but quickly stabilized; station JFNG showed significant fluctuations in the U direction around 13:00 UT; and station CKSV experienced similar fluctuations during the same period; station CMUM suffered minor disturbances in the U direction; while station URUM maintained relatively stable positioning throughout the storm, corresponding to steady VTEC variations. These findings demonstrate the substantial impact of ionospheric disturbances on GNSS positioning accuracy in southern and central China during the geomagnetic storm. This study reveals the complex and dynamic processes of ionospheric disturbances over China during the 1–2 December 2023 storm, highlighting the importance of ionospheric monitoring and high-precision positioning corrections during geomagnetic storms. The results provide scientific implications for improving GNSS positioning stability in mid- and low-latitude regions.

Abstract. The ionospheric response at middle and high latitudes in the Antarctica American and Australian sectors to the 26–27 September 2011 moderately intense geomagnetic storm was investigated using instruments including an ionosonde, riometer, and GNSS receivers. The multi-instrument observations permitted us to characterize the ionospheric storm-enhanced density (SED) and tongues of ionization (TOIs) as a function of storm time and location, considering the effect of prompt penetration electric fields (PPEFs). During the main phase of the geomagnetic storm, dayside SEDs were observed at middle latitudes, and in the nightside only density depletions were observed from middle to high latitudes. Both the increase and decrease in ionospheric density at middle latitudes can be attributed to a combination of processes, including the PPEF effect just after the storm onset, dominated by disturbance dynamo processes during the evolution of the main phase. Two SEDs–TOIs were identified in the Southern Hemisphere, but only the first episode had a counterpart in the Northern Hemisphere. This difference can be explained by the interhemispheric asymmetry caused by the high-latitude coupling between solar wind and the magnetosphere, which drives the dawn-to-dusk component of the interplanetary magnetic field. The formation of polar TOI is a function of the SED plume location that might be near the dayside cusp from which it can enter the polar cap, which was the case in the Southern Hemisphere. Strong GNSS scintillations were observed at stations collocated with SED plumes at middle latitudes and cusp on the dayside and at polar cap TOIs on the nightside.

In this paper, we analyze the characteristics of the induced geoelectric field in mainland China during the extreme magnetic storm from May 10–12 2024, based on the data from China Geoelectric Network. Our analysis focuses on the magnitude of the induced geoelectric field changes, the ratio between isotropic short and long dipoles, and the variation in polarization direction across different regions during the sudden onset of the magnetic storm. Our study reveals that horizontal changes in the induced geoelectric field intensity are not confined to specific regions during the sudden onset magnetic storms. When analyzing the same-direction ratio, at most stations it showed a consistent ratio between short and long dipoles. The polarization orientation derived from long-dipole ratios suggests that there is no consistent alignment of land and sea directions on the ground surface. These results indicate that the variations in geoelectric field measurements are influenced by the underlying electrical structure at each station. These findings are further interpreted by using high-density electric exploration data. This paper provides a quantitative characterization of changes in the induced geoelectric field intensity across mainland China during the geomagnetic storms, offering a foundation for further analysis of regional geoelectric field electromagnetic phenomena.

Abstract. This paper describes the ionospheric response to a geomagnetic storm beginning on 17 April 2002. We present the measurements of ionospheric parameters in the F-region obtained by the network of eight incoherent scatter radars. The main effects of this storm include a deep decrease in the electron density observed at high and middle latitudes in the pre-noon sector, and a minor enhancement in the density observed in the daytime sector at middle latitudes. Extreme plasma heating (>1000-3000 K) is observed at high latitudes, subsiding to 200-300K at subauroral latitudes. The western hemisphere radar chain observed the prompt penetration of the electric field from auroral to equatorial latitudes, as well as the daytime enhancement of plasma drift parallel to the magnetic field line, which is related to the enhancement in the equatorward winds. We suggest that in the first several hours after the storm onset, a negative phase above Millstone Hill (pre-noon sector) results from counteracting processes - penetration electric field, meridional wind, and electrodynamic heating, with electrodynamic heating being the dominant mechanism. At the lower latitude in the pre-noon sector (Arecibo and Jicamarca), the penetration electric field becomes more important, leading to a negative storm phase over Arecibo. In contrast, in the afternoon sector at mid-latitudes (Kharkov, Irkutsk), effects of penetration electric field and meridional wind do not counteract, but add up, leading to a small (~15%), positive storm phase over these locations. As the storm develops, Millstone Hill and Irkutsk mid-latitude radars observe further depletion of electron density due to the changes in the neutral composition.

The history of geomagnetism is more than 400 years old. Geomagnetic storms as we know them were discovered about 210 years ago. There has been keen interest in understanding Sun–Earth connection events, such as solar flares, CMEs, and concomitant magnetic storms in recent times. Magnetic storms are the most important component of space weather effects on Earth. We give an overview of the historical aspects of geomagnetic storms and the progress made during the past two centuries. Super magnetic storms can cause life-threatening power outages and satellite damage, communication failures and navigational problems. The data for such super magnetic storms that occurred in the last 50 years during the space era is sparce. Research on historical geomagnetic storms can help to create a database for intense and super magnetic storms. New knowledge of interplanetary and solar causes of magnetic storms gained from spaceage observations will be used to review the super magnetic storm of September 1–2, 1859. We discuss the occurrence probability of such super magnetic storms, and the maximum possible intensity for the effects of a perfect ICME: extreme super magnetic storm, extreme magnetospheric compression, and extreme magnetospheric electric fields.

We have analyzed spatial and temporal variations in ionospheric parameters over high and middle latitudes of Eurasia, using data from chains of high- and mid-latitude ionosondes during a severe magnetic storm in March 2015. To analyze the ionospheric response to the severe geomagnetic disturbance of solar cycle 24, we have employed ionosonde data on hourly average values of the critical frequency foF2 of the ionospheric F2 layer, the critical frequency of the sporadic layer foEs, and the minimum reflection frequency fmin. There are strong latitudinal and longitudinal differences between the features of temporal variations in the analyzed ionospheric parameters both under quiet conditions before the magnetic storm onset and during the storm. We discuss possible causes of the observed spatial variations in ionospheric parameters. The source of spatio-temporal variations in ionospheric ionization parameters may be inhomogeneities generated in the high-latitude ionosphere under conditions of increased helio-geomagnetic activity. During the magnetic storm main and recovery phases, periods of blackouts of radio signals from ionosondes were observed at both high and middle latitudes. During these periods, there was a significant increase in the absorption of radio waves used in ionosonde sounding, as well as in the frequency of occurrence of screening sporadic Es layers. The long-term effect of the negative ionospheric storm over high and middle latitudes of Europe is explained by the movement of the vast region of the reduced density ratio [O]/[N2] at thermosphere heights from the Far East and Siberia westward to Europe during the late recovery phase of the magnetic storm. Increased ionization of the ionospheric F2 layer with foF2 exceeding the level for quiet days before the onset of the magnetic disturbance over the vast region of Eastern, Western Siberia and Eastern Europe after the end of the magnetic storm in March 2015 is a manifestation of the aftereffect of magnetic storms. The increase in ionization was especially pronounced, as measured by the chain of mid-latitude ionosondes.

Abstract. Multi-diagnostic observations, covering a significant area of northwest Europe, were made during the magnetic storm interval (28–29 April 2001) that occurred during the High Rate SolarMax IGS/GPS-campaign. HF radio observations were made with vertical sounders (St. Petersburg and Sodankyla), oblique incidence sounders (OIS), on paths from Murmansk to St. Petersburg, 1050 km, and Inskip to Leicester, 170 km, Doppler sounders, on paths from Cyprus to St. Petersburg, 2800 km, and Murmansk to St. Petersburg, and a coherent scatter radar (CUTLASS, Hankasalmi, Finland). These, together with total electron content (TEC) measurements made at GPS stations from the Euref network in northwest Europe, are presented in this paper. A broad comparison of radio propagation data with ionospheric data at high and mid latitudes, under quiet and disturbed conditions, was undertaken. This analysis, together with a geophysical interpretation, allow us to better understand the nature of the ionospheric processes which occur during geomagnetic storms. The peculiarity of the storm was that it comprised of three individual substorms, the first of which appears to have been triggered by a compression of the magnetosphere. Besides the storm effects, we have also studied substorm effects in the observations separately, providing an improved understanding of the storm/substorm relationship. The main results of the investigations are the following. A narrow trough is formed some 10h after the storm onset in the TEC which is most likely a result of enhanced ionospheric convection. An enhancement in TEC some 2–3 h after the storm onset is most likely a result of heating and upwelling of the auroral ionosphere caused by enhanced currents. The so-called main effect on ionospheric propagation was observed at mid-latitudes during the first two substorms, but only during the first substorm at high latitudes. Ionospheric irregularities observed by CUTLASS were clearly related to the gradient in TEC associated with the trough. The oblique sounder and Doppler observations also demonstrate differences between the mid-latitude and high-latitude paths during this particular storm. Keywords. Ionosphere (Ionospheric disturbances) – Magnetospheric physics (Storms and substorms) – Radio science (Ionospheric propagation)

This study explores the ionospheric response over the Indian sector to the G4‐class geomagnetic storm of 23–24 April 2023. Utilizing multi‐instrument observations and SAMI2 modeling, ionospheric behavior was examined during the storm's main phase (17:41 UT, 23 April–04:03 UT, April 24) and the recovery phase (04:03 UT–22:44 UT, 24 April). During the main phase, ionosonde data from Tirunelveli showed rapid F‐layer height (h’F) variations driven by westward and eastward prompt penetration electric fields (PPEFs). The westward PPEF, induced by undershielding, led to an initial decrease in h’F followed by an increase, suppressing pre‐existing Equatorial Plasma Bubbles (EPBs) within two hours of the storm's onset. Despite a late‐night rise in h’F due to overshielding, no new EPB formed. The recovery phase exhibited a positive storm effect at low latitudes and a negative effect at higher latitudes, linked to disturbance dynamo electric fields (DDEFs) and thermospheric composition changes (Σ[O]/[N2] ratio). Large‐scale traveling ionospheric disturbances were clearly evident in GNSS TEC and ionosonde data, with a ∼2‐hr period, ∼2,450 km wavelength, and ∼340 m/s equatorward speed, likely driven by auroral/Joule heating‐induced atmospheric gravity waves. On 24 April, the westward DDEF suppressed the daytime equatorial ionization anomaly (EIA) and inhibited post‐sunset EPBs, while eastward DDEF increased h’F in the post‐midnight without EPB formation. We speculate that this absence might be due to a lack of seeding mechanisms. SAMI2 simulations incorporating E × B drift data reproduced several storm‐time features in the main and recovery phases.

We present a study of the morphology, patterns, and dynamics of dust storms on Mars observed at the edge of the North Polar cap during the Northern Hemisphere Spring Equinox from May to June 2019 (MY35) [1] and of the onset of the Global Dust Storm in May to June 2018 (MY34) [2]. The analysis is based on images obtained by the Visual Monitoring Camera (VMC) [3] and the High Resolution Stereo Camera (HRSC) [4] onboard Mars Express, and MARCI camera onboard Mars Reconnaissance Orbiter (MRO) [5-6]. VMC images were analyzed with tools described in previous works [7-8], HRSC images were analyzed from map-projections, and MARCI were processed and projected using the Integrated Software for Imagers and Spectrometers (ISIS) of the USGS [9].The dust activity at the edge on the North Polar cap in MY35 (Ls = 28°-35°) took place around latitude 60°N in the longitude range 140°E -240°E (along Acidalia, Arcadia and Amazonis planitias). These features exhibited a rich phenomenology typical of this season with different morphologies in form of filaments and fronts, flushing storms (large arc-shaped features), compact textured storms and well developed spiral systems, sometimes mixed with water-ice clouds [1]. Here we concentrate in these last two types of features.The textured and spiral storms are of local type (areas < 1.6x106 km2)and contained cellular patterns suggestive of organized active updrafts within the storms. The cells varied in size from one storm to other: 50x20 km, 135x60 km and 70x40 km. In all cases, the cell texture is anisotropic in the horizontal size (length/width, l/w~ 2) with values well above the atmospheric scale height (H ~ 8 km). Measured local winds reached velocities from 20 to 45 ms-1. The presence of storms with such different overall structure, for example in the form of compact areas on the one hand and spiral systems on the other, indicates that the underlying mechanisms are different but that above a threshold velocity, all of them generate the dust storms. We explore the action of dry convection in the formation of these patterns driven by buoyancy generated by the radiative heating of atmospheric dust.The onset of the last Global Dust Storm (GDS 2018) took place on 30 May 2018 (Ls = 182°) at latitude ~ 33°N and longitude 342°E, following a precursor storm on 26-27 May 2018 at latitude ~ 58°N and longitude 325°E [2]. The MARCI high-resolution images reveal again the presence of cellular patterns at different scales (typically 40x20 km) with a well defined frontal line marking the storm advance. The storm morphology rapidly evolved in one day showing patterns of long wave trains with wavelengths ranging from 10 to 20 km. We interpret these as gravity waves formed by intense winds flowing over craters and other topographic structures. 

Understanding extreme space weather events is of paramount importance in efforts to protect technological systems in space and on the ground. Particularly in the thermosphere, the subsequent extreme magnetic storms can pose serious threats to low Earth orbit (LEO) spacecraft by intensifying errors in orbit predictions. Extreme magnetic storms (minimum Dst ≤ − 250 nT) are extremely rare: Only seven events occurred during the era of spacecraft with high‐level accelerometers such as CHAMP (CHAllenge Minisatellite Payload) and GRACE (Gravity Recovery And Climate experiment) and none with minimum Dst ≤ − 500 nT, here termed magnetic superstorms. Therefore, current knowledge of thermospheric mass density response to superstorms is very limited. Thus, in order to advance this knowledge, four known magnetic superstorms in history, that is, events occurring before CHAMP's and GRACE's commission times, with complete data sets, are used to empirically estimate density enhancements and subsequent orbital drag. The November 2003 magnetic storm (minimum Dst = − 422 nT), the most extreme event observed by both satellites, is used as the benchmark event. Results show that, as expected, orbital degradation is more severe for the most intense storms. Additionally, results clearly point out that the time duration of the storm is strongly associated with storm time orbital drag effects, being as important as or even more important than storm intensity itself. The most extreme storm time decays during CHAMP/GRACE‐like sample satellite orbits estimated for the March 1989 magnetic superstorm show that long‐lasting superstorms can have highly detrimental consequences for the orbital dynamics of satellites in LEO.

The main idea of the present study is to investigate in detail the time evolution of the spatial inhomogeneities connected with the ionospheric response to the geomagnetic storm registered in the period of 10–11 May 2024. The obtained ionospheric anomalies represented by the relative deviations of the global Total Electron Content (TEC) data have been utilized in the analysis. The used global TEC data have been converted to a coordinate system with a modip latitude and geographical longitude. In addition to the maps illustrating the global spatial distribution of the geomagnetically forced ionospheric anomalies, a presentation of the observed longitudinal structures by sinusoidal approximation has also been used. The resulting positive and negative responses have been studied depending on the magnetic latitude, local times and the behavior of the geomagnetic activity parameters during the considered event. The interpretation takes into account the known mechanisms for the effect of the geomagnetic storm on the electron density. A special attention is focused on the differences in the two hemispheres at high and mid latitudes, where a simultaneous direct impact of the particle precipitation and the change in the temperature regime of the neutral atmosphere has been assumed. The low-latitude response as a result of the Equatorial Ionization Anomaly (EIA) associated with Disturbed Dynamo Electric Fields (DDEFs) and its relationship with local time has also been considered.

The ionospheric response to a geomagnetic storm is a geophysical process. Although strong geomagnetic storms input more energy into the Earth’s upper atmosphere, the ionospheric response often does not reflect the same level of variation as the geomagnetic storm, and the response may be weak during a very strong storm. However, the estimated ionospheric response to geomagnetic activity also varies with extraction method. Here, two different methods—the spectral whitening method (SWM) and the monthly median method (MMM)—are used to verify whether the apparent weak ionospheric response is an artifact of the processing method. The weak ionospheric response is found with both methods, which suggests it is a real ionospheric phenomenon. The statistical characteristics of the regional and global ionospheric weak response to a super geomagnetic storm (SGS) and to an SGS with a preceding storm event (SGS-PRE) are investigated and compared. The results show that the regional ionospheric weak response to an SGS is more prevalent at middle latitudes than those at low and high latitudes. The global ionospheric weak response occurs more frequently under high solar activity and has a strong correlation with SGS-PRE, which suggests that the effect of a storm on the ionosphere can be influenced by its preconditioning, especially when there is an earlier storm and the time interval between the two storms is short. In fact, an ionospheric long-lasting disturbance may be an important reason for the ionospheric weak response caused by the SGS-PRE.

This article describes the results of monitoring the radiation situation in a medium circular orbit, obtained from the data of the experimental dose control complex (EDCC) of the spacecraft, developed by JSC “Reshetnev”, with a circular orbit at an altitude of H=8070 km. The article compares the experimentally obtained EDCC data with the calculated data, obtained during flight operation over two years of research. It should be noted that this orbit is poorly studied by Russian spacecraft developers in terms of the impact of space factors. Also considers the effect of the extreme geomagnetic disturbance in May 2024 on the rate of accumulation of the absorbed dose. The method of conducting the experiment consists of creating different conditions of mass protection for each of the nine sensors. The mass protection is varied by installing a steel grid with different cell thicknesses. Thus, each sensitive element is in unique irradiation conditions – mass protection weakens the flux of ionizing radiation and changes its spectrum (differently for each type of radiation). When developing a new type of orbit for spacecraft operation, the task of ensuring the resistance of onboard equipment and the spacecraft as a whole to the effects of ionizing radiation factors of outer space, typical for this orbit, is relevant. For this, experimental confirmation or refinement of the calculated radiation model of impact based on the obtained in-kind data is necessary. The main task solved in the article is to monitor the levels of the integral accumulated dose behind various protections when exposed to ionizing radiation of outer space at an orbit of 8070 km and to compare the results of experimental data with the calculated estimates carried out according to OST134-1044-2007. The article reflects the results of long-term measurements of the absorbed dose of ionizing radiation for a spacecraft with such an orbit. As a result of the measurements, it was established that after an extreme magnetic storm, there is a significant increase in the rate of dose accumulation. This led to the dose recorded for 722 days exceeding the calculated valueю.

The storm onset on 7 September 2017, triggered several variations in the ionospheric electron density, causing severe phase fluctuations at polar latitudes in both hemispheres. In addition, although quite rare at high latitudes, clear amplitude scintillations were recorded by two Global Navigation Satellite System receivers during the main phase of the storm. This work attempted to investigate the physical mechanisms triggering the observed amplitude scintillations, with the aim of identifying the conditions favoring such events. We investigated the ionospheric background and other conditions that prevailed when the irregularities formed and moved, following a multi-observations approach. Specifically, we combined information from scintillation parameters and recorded by multi-constellation (GPS, GLONASS and Galileo) receivers located at Concordia station (75.10°S, 123.35°E) and SANAE IV base (71.67°S, 2.84°W), with measurements acquired by the Special Sensor Ultraviolet Spectrographic Imager on board the Defense Meteorological Satellite Program satellites, the Super Dual Auroral Radar Network, the Swarm constellation and ground-based magnetometers. Besides confirming the high degree of complexity of the ionospheric dynamics, our multi-instrument observation identified the physical conditions that likely favor the occurrence of amplitude scintillations at high latitudes. Results suggest that the necessary conditions for the observation of this type of scintillation in high-latitude regions are high levels of ionization and a strong variability of plasma dynamics. Both of these conditions are typically featured during high solar activity.