The geomagnetic storm occurred on 25 August 2018, i.e. during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo‐Electromagnetic Satellite (CSES‐01). By integrating the in situ measurements provided by CSES‐01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca. 470 km) with ground‐based observations (ionosondes, magnetometers and Global Navigation Satellite System receivers), we investigate the ionospheric response at low‐ and mid‐ latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the Equatorial Electrojet (EEJ). Our proposed multi‐sensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between Prompt Penetrating Electric Fields and Disturbance Dynamo Electric Fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES‐01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter‐EEJ during both 25 and 26 August at Brazilian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES‐01/Swarm altitudes integrated with the ground‐based observation recorded signatures of Equatorial Ionospheric Anomaly (EIA) crests formation and modification during daytime coupled with the positive ionospheric storm effects at mid‐latitude.

The series of X and M class flares and associated coronal mass ejections that occurred on the first days of September 2017 induced significant perturbations on the low‐latitude ionospheric electrodynamics. On 8 September in the Indian sector, the storm caused a severe modification of the equatorial electrojet (EEJ) with a consequent variation of the ionospheric structuring and dynamics. In our analysis, we propose an original method to isolate and identify EEJ variations from geomagnetic data and we detect the presence of equatorial plasma bubbles (EPB) from L‐band total electron content (TEC) data in order to understand their movement. Our results provide evidence of independent EPBs appearance freshly generated and inherited from a migrating plasma structure. The EPB (or EPBs) occurring in the south of India is/are freshly generated just above the magnetic equator, and is/are likely triggered by the sudden increase of EEJ just before the local sunset, acting as a pre‐reversal enhancement. The EPB appearing in the North‐East Indian region is associated with a migrating structure, resulting in a northward movement with a velocity of about 650 m/s, possibly testifying the passage of a large‐scale traveling ionospheric disturbance. The occurrence of severe post‐sunset scintillations in the northeastern sector suggests a possible cascade process forming small‐scale irregularities from the migrating EPB.

On 3 November 2021, an interplanetary coronal mass ejection impacted the Earth’s magnetosphere leading to a relevant geomagnetic storm (Kp = 8-), the most intense event that occurred so far during the rising phase of solar cycle 25. This work presents the state of the solar wind before and during the geomagnetic storm, as well as the response of the plasmasphere–ionosphere–thermosphere system in the European sector. To investigate the longitudinal differences, the ionosphere–thermosphere response of the American sector was also analyzed. The plasmasphere dynamics was investigated through field line resonances detected at the European quasi-Meridional Magnetometer Array, while the ionosphere was investigated through the combined use of ionospheric parameters (mainly the critical frequency of the F2 layer, foF2) from ionosondes and Total Electron Content (TEC) obtained from Global Navigation Satellite System receivers at four locations in the European sector, and at three locations in the American one. An original method was used to retrieve aeronomic parameters from observed electron concentration in the ionospheric F region. During the analyzed interval, the plasmasphere, originally in a state of saturation, was eroded up to two Earth’s radii, and only partially recovered after the main phase of the storm. The possible formation of a drainage plume is also observed. We observed variations in the ionospheric parameters with negative and positive phase and reported longitudinal and latitudinal dependence of storm features in the European sector. The relative behavior between foF2 and TEC data is also discussed in order to speculate about the possible role of the topside ionosphere and plasmasphere response at the investigated European site. The American sector analysis revealed negative storm signatures in electron concentration at the F2 region. Neutral composition and temperature changes are shown to be the main reason for the observed decrease of electron concentration in the American sector.

This study is focused to investigate the Pc5 geomagnetic pulsations in response to the solar wind forcing and their relationship with the relativistic electron flux at geostationary orbit. We analyzed the correlation of the Pc5 power in the magnetosphere and on the ground, at low and high latitude, with the solar wind speed and fluctuation power of the interplanetary magnetic field and solar wind dynamic pressure through the years 2006 to 2010, also examining the relative timing between pulsations and solar wind parameters. We found a very significant correlation of the Pc5 power with simultaneous solar wind pressure fluctuations and with the solar wind speed lagged by several hours; the relative amplitude of the two correlation peaks depending on the solar cycle phase and on the latitude.