A Simulation Study of the Equatorial Ionospheric Response to the October 2013 Geomagnetic Storm

Abstract

AbstractThe ionospheric observation from ionosonde at Sao Luis (2.5°S, 44.2°W; 6.68°S dip latitude) around the magnetic equator showed that the nighttime ionospheric F2 layer was uplifted by more than 150 km during the October 2013 geomagnetic storm. The changes of the F2 peak height (hmF2) at the magnetic equator were generally attributed to the variations of vertical drift associated with zonal electric fields. In this paper, the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulation results are utilized to explore the possible physical mechanisms responsible for the observed increase of hmF2 at Sao Luis. The TIEGCM generally reproduced the changes of F2 peak electron density (NmF2) and its height (hmF2) during the main and recovery phases of the October 2013 storm. A series of controlled simulations revealed that storm time hmF2 changes at the magnetic equator are not purely associated with the changes of electric fields; horizontal plasma transport due to meridional winds and thermospheric expansion also contributed significantly to the profound increase of nighttime hmF2 observed at Sao Luis on 2 October. Moreover, the changes of meridional winds and neutral temperature in the equatorial region are associated with storm time traveling atmospheric disturbances originating from high latitudes.