Modeling seasonal variations of auroral particle precipitation in a global-scale magnetosphere-ionosphere simulation

In this paper we examine how these variations are modeled in the Lyon-Fedder-Mobarry (LFM) global-scale magnetohydrodynamic simulation of the coupled solar wind-magnetosphere-ionosphere system. In order to account for changes in the solar wind conditions caused by the seasonal variation of the Earth's dipole tilt we carefully select the solar wind parameters so that the effective driving conditions are the same across the March, June, and December intervals examined.

The seasonal variation of the field-aligned current strengths is in good agreement with observations, with the sunlit hemisphere having more current than the dark hemisphere in the June and December intervals. However, in order to bring the modeled precipitating electron energy flux into better agreement with the observations we need to utilize a modified current-voltage relationship which includes a proxy for illumination effects.