Reconnection layer at the flank magnetopause in the presence of shear flow

Abstract

We present hybrid simulations of reconnection layer at the flank magnetopause, where a large plasma flow speed is present in the magnetosheath. It is found that there exists a threshold flow speed υ* such that for the magnetosheath flow speed υs < υ* (υs > υ* ), the rotational discontinuity with a larger field rotation angle exists on the magnetosheath (magnetospheric) side of the reconnection layer. The threshold speed is found to be υ* = υAm ‐ υAs, where υAm (υAs) is the Alfvén speed on the magnetospheric (magnetosheath) side of the reconnection layer. Furthermore, for υs << υ*, the rotational discontinuity on the magnetosheath side is very thin, and an accelerated high‐speed flow is located earthward of the rotational discontinuity, as observed at the dayside magnetopause. For υs ∼ υ*, the magnetic field transition region is thick, and the accelerated flow is present in the entire field transition region, as observed at the flank magnetopause.