Formation of the magnetopause boundary layer by magnetic reconnection

Abstract

Magnetic reconnection at the earth's magnetopause can lead to the formation of the magnetopause boundary layer. In this paper, our recent hybrid simulations of the structure of this reconnection layer are summarized. The results are compared with those from the ideal MHD formulation and resistive MHD simulations. In the ideal MHD, rotational discontinuities, slow shocks, slow expansion waves, and contact discontinuity are present in the reconnection layer. In the resistive MHD simulation, the rotational discontinuity is replaced by an intermediate shock or time-dependent intermediate shock (TDIS). In the hybrid simulation, the TDIS quickly evolves to a steady rotational discontinuity. The contact discontinuity cannot be identified due to the mixing of ions from the magnetosheath and magnetosphere, and slow shocks and slow expansion waves are modified. At the dayside magnetopause, a thin rotational discontinuity bounds the reconnection layer from the magnetosheath side, and a high-speed accelerated plasma flow is present on the magnetospheric side of the rotational discontinuity. At the flank of the magnetopause, where a large plasma flow is present in the magnetosheath, the magnetic field transition region is thick, and the accelerated flow exists in the entire field transition region.