On 4 February 2022, 38 Starlink satellites were destroyed by the geomagnetic storm, which brought significant financial, aerospace and public influences. In this letter, we reveal the space weather process during 3–4 February 2022 geomagnetic disturbances, from the Sun all the way to the satellite orbiting atmosphere. Initiated by an M1.0 class flare and the following coronal mass ejection (CME), a moderate geomagnetic storm was stimulated on 3rd February by the CME arrival at Earth. Subsequently, another moderate storm was triggered on 4th February by the passage of another CME. Model simulations driven by solar wind show that the first geomagnetic storm induced around 20% atmospheric density perturbations at 210 km altitude on 3rd February. The unexpected subsequent storm on 4th February led to a density enhancement of around 20%–30% at around 210 km. The resulting atmospheric drag can be even larger, since the regional density enhancement was over 60% and the satellite orbits were continuously decaying. This event brings forth the urgent requirements of better understanding and accurate prediction of the space weather as well as collaborations between industry and space weather community.

In this study, multiple data sets from Beidou geostationary orbit satellites total electron contents (TECs), ionosonde, meteor radar, magnetometer, and model simulations have been used to investigate the ionospheric responses in the Asian‐Australian sector during the September 2017 geomagnetic storm. It was found that long‐duration daytime TEC enhancements that lasted from 7 to 12 September 2017 were observed by the Beidou geostationary orbit satellite constellation. This is a unique event as the prominent TEC enhancements persisted during the storm recovery phase when geomagnetic activity became quiet. The Thermosphere‐Ionosphere Electrodynamics Global Circulation Model predicted that the TEC enhancements on 7–9 September were associated with the geomagnetic activity, but it showed significant electron density depletions on 10 and 11 September in contrast to the observed TEC enhancements. Our results suggested that the observed long‐duration TEC enhancements from 7 to 12 September are mainly associated with the interplay of ionospheric dynamics and electrodynamics. Nevertheless, the root causes for the observed TEC enhancements seen in the storm recovery phase are unknown and require further observations and model studies.

On 21 June 2020, an annular solar eclipse will traverse the low latitudes from Africa to Southeast Asia. The highest latitude of the maximum eclipse obscuration is approximately 30°. This low-latitude solar eclipse provides a unique and unprecedented opportunity to explore the impact of the eclipse on the low-latitude ionosphere–thermosphere (I–T) system, especially in the equatorial ionization anomaly region. In this study, we describe a quantitative prediction of the impact of this upcoming solar eclipse on the I–T system by using Thermosphere–Ionosphere–Electrodynamics General Circulation Model simulations. A prominent total electron content (TEC) enhancement of around 2 TEC units occurs in the equatorial ionization anomaly region even when this region is still in the shadow of the eclipse. This TEC enhancement lasts for nearly 4.5 hours, long after the solar eclipse has ended. Further model control simulations indicate that the TEC increase is mainly caused by the eclipse-induced transequatorial plasma transport associated with northward neutral wind perturbations, which result from eclipse-induced pressure gradient changes. The results illustrate that the effect of the solar eclipse on the I–T system is not transient and linear but should be considered a dynamically and energetically coupled system.

In this study, the in situ electron density measurements from the Challenging Minisatellite Payload (CHAMP) and solar extreme ultraviolet (EUV) radiation from the Solar Extreme Ultraviolet Experiment instrument on board the Thermosphere Ionosphere Mesosphere Energetic and Dynamics satellite, both with a time resolution of 1.5 hr, are used to explore the peak response of the ionospheric F₂ region plasma to the peak of 27‐day solar EUV flux variation. The time delays of in situ electron density changes obtained from the CHAMP satellite in response to 27‐day solar EUV flux changes vary from 0 to about 3 days. Meanwhile, the Thermosphere Ionosphere Electrodynamics General Circulation Model simulations driven by the measured EUV flux and the actual geomagnetic activity show similar time delays as those observed in the CHAMP measurements. Further simulations reveal that the geomagnetic activity greatly affects the determination of the ionospheric time delay to the 27‐day solar EUV flux variations. Besides, the solar zenith angle change within the solar rotation interval can cause large latitudinal differences in the time delay. The ionospheric time delay to the pure 27‐day solar EUV flux variation is less than 1 day and slightly increases with latitude, when geomagnetic activity and seasonal variations are eliminated in the simulation. The simulation results further suggest that the ionospheric response time is associated with the photochemical, dynamic, and electrodynamic processes in the ionosphere‐thermosphere system.

The low‐latitude ionospheric TEC observed by the Beidou geostationary satellite showed large enhancement during 27–30 August 2018 of the storm recovery phase. The cause of the positive ionospheric storm during the recovery phase has yet to be resolved. In this study, multiple observations, including aurora, high‐latitude convection, potential, and the TEC maps, were used to study the contributions from the high‐speed solar wind to the ionosphere during the recovery phase of the storm. It was found that the high‐speed solar wind was effective in modulating the intensity and the size of the auroral oval, high‐latitude convection, and potential pattern. The Thermosphere Ionosphere Electrodynamics General Circulation Model generally reproduced the observed evolution of the ionosphere at high latitudes during the recovery phase of the storm, and it was used to quantitatively investigate the effects of the high‐speed solar wind on the recovery phase ionosphere. The results suggested that the high‐speed solar wind caused increase of TEC at auroral oval was about 2 TECU. The high‐speed solar wind, combined with oscillating interplanetary magnetic field Bz, led to the enhancement of the low‐latitude prompt penetrating electric fields and increased the low‐latitude TEC of about 2 TECU. Therefore, the high‐speed solar wind was a possible driver to the ionospheric positive storm during the recovery phase, but the causes for the more than 10‐TECU enhancement at low and middle latitudes during the recovery phase of this event are unknown.

In this study, the ionospheric responses in the Asian‐Australian, American, and African sectors during the August 2018 geomagnetic storm were investigated based on the Beidou geostationary orbit (GEO) satellite and Massachusetts Institute of Technology (MIT) Madrigal total electron contents (TECs), combined with measurements from ionosondes, magnetometers, and Global Ultraviolet Imager (GUVI). The middle‐ and low‐latitude TECs were dominated by positive responses over the three longitudinal sectors during the storm on 26–29 August. It is unique that daytime TECs at the Asian‐Australian, American, and African sectors displayed large enhancements larger than 10 TEC units (TECu) on 27–29 August, during the recovery phase, when the ionosphere is usually dominated by plasma depletions due to the ionospheric disturbance dynamo and/or disturbed thermospheric compositions. The combination and competition of the disturbed vertical plasma drifts through the solar wind‐magnetosphere‐ionosphere (SW‐M‐I) coupling and disturbed neutral compositions contribute significantly to the daytime TEC responses at different longitudinal sectors on 26 August during the main and early recovery phases. The eastward equatorial electrojet and O/N₂ during the recovery phase on 27–29 August are larger than the quiet reference, which suggest that the enhanced upward vertical plasma drifts combining with higher O/N₂ make an important contribution on the daytime positive ionospheric storm during the recovery phase. The enhanced vertical plasma drifts could not be driven by the SW‐M‐I coupling or ionospheric disturbance dynamo associated with the geomagnetic storm. Further studies should be untaken to explore the dominant sources for the enhanced upward vertical drifts during the recovery phase.