Dipole tilt control of the magnetopause for southward IMF from global magnetohydrodynamic simulations

摘要

Numerical results from a physics-based global magnetohydrodynamic (MHD) model are used to examine the effect of the dipole tilt angle(y)on the location and shape of the magnetopause. Identification of the magnetopause location in the simulation domain is automated using criteria based on the current density and the shape of the streamlines. These data are fitted with a three-dimensional surface controlled by 10 configuration parameters which allow description of the cusp geometry as well as the asymmetry in the Z direction and the azimuthal asymmetry of the magnetopause. Effects of dipole tilt angle on the configuration parameters are analyzed from a series of simulations for southward IMF and different dipole tilt angle values. It is found that dipole tilt angle has little impact on the equatorial magnetopause but significantly affects the cusp locations and the degree of asymmetry between the Northern and Southern hemispheres and the equatorial/ meridional plane. The results are shown to be consistent with three frequently used empirical models derived from satellite observations.