Effects of the dipole tilt and northward and duskward IMF on dayside magnetic reconnection in a global MHD simulation

Abstract

By using a three‐dimensional global magnetohydrodynamic simulation of the Earth's magnetosphere, we have studied whether antiparallel or subsolar reconnection better describes magnetospheric dynamics at the dayside magnetopause for the case of northward and duskward interplanetary magnetic field (IMF) and a positive dipole tilt. The simulation shows that the reconnection dominantly occurs at high latitudes where antiparallel field regions appear in the northern dusk sector and in the southern dawn sector. For the northward and duskward IMF case of 30° dipole tilt, the reconnection region in the dusk sector moves tailward at high magnetic latitudes in the Northern Hemisphere along the magnetopause further than that for the southward IMF case. Both the convective electric field and the resistive electric field are peaked in the region where the field lines are antiparallel. Moreover the perpendicular and parallel components of the current in the antiparallel field region are greater than those of the current in the subsolar and magnetic equator regions. The field‐aligned current, in the Southern (winter) Hemisphere on the dawn region is stronger than that in the Northern (summer) Hemisphere on the dusk region because the reconnection site shifts toward the tail in the winter hemisphere, which is just opposite to the case of southward IMF studied by Park et al. (2006). In the Northern (summer) Hemisphere, a three‐cell pattern appears in the ionosphere because the reconnection site shifts tailward and duskward from the cusp. In the Southern (winter) Hemisphere, the three‐cell pattern is distorted and has a weaker cross‐polar cap potential than that in the Northern Hemisphere due to the effects of the positive dipole tilt.