Ionospheric Response Over Brazil to the August 2018 Geomagnetic Storm as Probed by CSES-01 and Swarm Satellites and by Local Ground-Based Observations

The geomagnetic storm that occurred on 25 August 25 2018, that is, 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., 460 km) with ground-based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower- 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 multisensor 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 Braziliian 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 crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude.