X-line sliding in an asymmetric ion flow

We have carried out two-dimensional full-particle simulations of an asymmetric current sheet (like the Earth's magnetopause) with a reconnected layer. When the ion flows cross obliquely the X-line, the X-line starts to slide with its speed comparable to the ion flow at the X-line. If (1) Stagnation point of the ion flows are decoupled from the X-line, and (2) Those flows form an oblique pattern about the X-line, the sufficient condition of the X-line sliding is concluded. The presence of an anti-parallel shear flow along the current sheet, or an out-of-plane guide field is found to settle that condition.