Simulating electron and ion temperature in a global ionosphere thermosphere model: Validation and modeling an idealized substorm

Abstract

Electron and ion temperatures control many chemical and physical processes in the ionosphere–thermosphere system. Recently, improved electron and ion energy equations were implemented in the Global Ionosphere Thermosphere Model (GITM). The source energy of the electron temperature (Te) includes thermal conduction, heating due to photoionization, elastic collisions with ions, elastic and inelastic collisions with neutrals, auroral precipitation, and heat flux from inner magnetosphere. The source terms in the ion temperature (Ti) equation include thermal conduction, and elastic collisions with electrons and neutrals. The new implementation of Te improved the ionospheric density at middle and high latitudes with respect to IRI. The improved GITM also reproduced the diurnal variation in Te and Ti observed by incoherent scatter radars at low and middle latitudes. The model was used to investigate an idealized substorm statistically described by Clausen et al. (2014). It was found that the responses of the E-region Ne and Te were highly correlated with the variation in auroral hemispheric power. The change of the F-region Te was correlated with the E-region Te and Ne, which was consistent with observations. The response of the F-region Ne to the particle precipitation was delayed by about 30min, and lasted significantly longer than the enhanced precipitation. The variations of Ti in both the E- and F-regions were dominated by IMF-driven ion drifts through frictional energy coupling with the neutrals. It was also found that the increase of the mid-latitude heat flux by one order of magnitude enhanced Te, electron density and TEC by up to 120%, 80% and 80% respectively between dusk and midnight.