Transient reconnection caused by the impact and switch-off of a transverse shear flow

Abstract

It is supposed that local and transient reconnection in the plasma boundary layer can be caused by the impact and switch-off of a single directional transverse shear flow. MHD (magnetohydrodynamic) simulation is used to investigate the reconnection processes in the two cases. It is found that if the inflow is homogeneous, it does not cause reconnection; if the inflow is shearing flow, no matter how great the shear of the flow is, it may cause reconnection either during impacting period or after stop impacting. It is pointed out that the sudden stop of external force may be an important triggering mechanism of energy transformation and reconnection in the plasma boundary layer region.

Reconnection Rate for the Inhomogeneous Resistivity Petschek Model

“…We were not able to reproduce Petschek regime using variation of MHD parameters at the upper boundary with homogeneous resistivity, a probably solution (Chen, 1999) of this problem either is essentially time-dependent or corresponds to the case of strong reconnection. According to our simulations, for Petschek state to exist a strongly localized resistivity is needed, and for the spatially homogeneous resistivity l d = L Sweet-Parker regime seems to be always the case.…”

“…For the case of localized resistivity l d practically coincides with the scale of the inhomogeneity of the conductivity. In principal, there might be a possibility to produce Petschek-type reconnection with constant resistivity using a highly inhomogeneous behaviour of the MHD parameters at the upper boundary (narrow stream, for example, see Chen et al,1999), and then l d has the meaning of the scale of this shearing flow or other boundary factor which causes the reconnection.…”