Magnetic Reconnection in the Solar Wind: An Update

Abstract

Magnetic reconnection in the solar wind commonly occurs in a quasi‐stationary mode. It produces extensive Petschek‐like exhausts of roughly Alfvénic jetting plasma typically bounded by back‐to‐back rotational discontinuities that bifurcate a reconnecting current sheet. It occurs most frequently at current sheets associated with relatively small (<90°) magnetic field rotations in low (<1) beta plasma. Reconnection exhausts are relatively common (typically 2–3 events/day at 1 AU) in the low‐speed wind and within interplanetary coronal mass ejections, and less common (0.6 events/day) in the Alfvénic turbulence characteristic of the high‐speed wind from coronal holes. Reconnection occurs relatively infrequently at the heliospheric current sheet, HCS, but observations of exhausts at the HCS are particularly revealing of the magnetic field topology changes associated with the reconnection process. Reconnection in the solar wind is not explosive—the magnetic energy release occurs over a long time interval following reconnection as the Alfvénic disturbances initiated by the process propagate into the surrounding solar wind plasma. There is as yet no good evidence to suggest that reconnection in the solar wind ever produces substantial particle acceleration beyond that associated with the bulk acceleration of the plasma.