IMF cone angle control of the magnetopause location: Statistical study

Abstract

We investigate the dependence of the magnetopause location on the interplanetary magnetic field (IMF) cone angle (the angle between the IMF and solar wind velocity vectors) in a statistical study based on ≈6500 magnetopause crossings observed by the five THEMIS spacecraft, both at the dayside and flanks. To remove other well-known effects, we analyze the difference between observed magnetopause radial distances and those predicted by an empirical magnetopause model (scalable by the solar wind dynamic pressure and IMF B Z component). The results demonstrate a systematic increase of the magnetopause distance for radial IMF directions, from 0.3 R E at 90° to 1.7 R E at 0 or 180° cone angle. Moreover, a stronger dependence of the magnetopause location on the solar wind dynamic pressure than predicted by the current models was observed. © 2010 by the American Geophysical Union.