Reconnection Separatrix: simulations and spacecraft measurements

We review the progress in understanding the processes near the separatrices during magnetic reconnection. The results are obtained from numerical simulation and spacecraft measurement. The reconnection separatrices represent the surface (cross curve in two-dimensional regime) separating the reconnected magnetic field lines from the reconnecting lines, and thereby connect to the reconnection X-line. The average properties of the particle distribution and physical processes in the separatrix region are summarized. Recent studies confirm that various instabilities occur in the separatrix region and lead to a complex interplay and affecting the plasma in this region. The microphysics in the separatrix region should play an important role in reconnection dynamics. Furthermore, electrons are accelerated up to 100 keV before they enter into the electron diffusion region: a significant part of energy conversion takes place in the separatrix region during reconnection.status: publishe