A modeling study of global ionospheric and thermospheric responses to extreme solar flare

Abstract

In this study, we employed a thermosphere and ionosphere coupling model to investigate ionospheric and thermospheric responses to an extreme solar flare of X40. The simulated results show that the peak enhancement of total electron content reaches about 35 TECU (total electron content unit, 1 TECU = 1016 el m-2), and there are as long as more than 4 h ionospheric disturbances induced by the extreme solar flare. At the same time, the extreme solar flare causes significant disturbances in the thermosphere. The peak enhancement of neutral density at 400 km reaches more than 100%, and the peak enhancement in neutral temperature at 400 km is about 250 K. Several numerical experiments for different class solar flares were further carried out to study the ionosphere and thermosphere variations with solar flare level. The results show that the increasing amplitude of electron density at low altitude decreases with increasing flare level; however, the increasing amplitude of electron density at topside ionosphere increases with increasing flare level. The thermosphere density has the same variation trends with flare level. These results suggest that the extreme solar flare would cause the strong disturbances at high height.