RESPONSE OF THE EQUATORIAL AND LOW LATITUDE IONOSPHERE OVER THE SOUTH AMERICAN SECTOR TO THE 4th February 2022 GEOMAGNETIC STORM

On the 4th day of February 2022 (DOY 35), a geomagnetic storm caused deorbiting of about 80% of low altitude Starlink satellites launched on a previous day providing evidences that the storm time neutral atmosphere expanded causing unexpected larger drag on the satellites. During this storm the Dst magnetic index reached about -52 nT on February 03, recovery to 0 level around midnight and reached about -50 nT on day 04, recovering to pre-storm values on day 05. Recurrent long lasting southward incursions of Bz were observed during these 3 days. The aim of this study is to provide the ionospheric response to this magnetic storm since the response of the neutral atmosphere was substantial even though this storm is classified as a weak one. This study utilizes statistical analysis and observations from TEC and geomagnetic indices to describe the response of the low latitude and equatorial ionosphere over South America to this geomagnetic storm in terms of variations in TEC. The stations of interest are Belém (1.18549o S, 48.53379o W) close to dip equator and Cachoeira Paulista (22.68352o S, 44.99492o W) under the Equatorial Ionization Anomaly region. Surprisingly the TEC presented just a small decrease on day 05 during the storm recovery phase compared with days 03 and 04 for both sites. Mechanisms responsible for this neutral atmosphere expansion during this storm are presented at this work.