Equatorial ionization anomaly and thermospheric meridional winds during two major storms over Brazilian low latitudes

Abstract The equatorial ionosphere responses over Brazil to two intense magnetic storms that occurred during 2001 are investigated. The equatorial ionization anomaly (EIA) and variations in the zonal electric field and meridional winds at different storms phases are studied using data collected by digisondes and GPS receivers. The difference between the F layer peak density ( foF2 ) at an equatorial and a low latitude sites was used to quantify the EIA; while the difference between the true heights ( h F ) at the equatorial and an off-equatorial site was used to calculate the magnetic meridional winds. The vertical drift was calculated as dh F / dt . The results show prompt penetration electric fields causing unusual early morning development of the EIA, and disturbed dynamo electric field producing significant modification in the F region parameters. Variations to different degrees in the vertical drift, the thermospheric meridional winds and the EIA developments were observed depending on the storm phases.