Null Points in Three-Dimensional Kinetic Simulations of Magnetic Reconnection

Abstract:

Kinetic particle-in-cell simulations are the primary tool for studying magnetic reconnection in space plasmas. Magnetic null points are believed to be the preferred locations in space where magnetic reconnection is luckily to happen, and are in the focus of interest of space missions such as Cluster and MMS. Simulations of magnetic reconnection in various configurations performed with the implicit particle-in-cell code iPic3D revealed that nulls are ubiquitious in these models. We apply the Poincare index technique to locate and identify the topological characteristics of the magnetic null points in different three-dimensional simulations. We investigate the relevance of magnetic nulls to energy dissipation, turbulence and plasma instabilities. In particular, we found out that magnetic nulls of spiral type associated with magnetic islands and flux ropes play more important role in the energy release than the radial nulls. This finding is in accordance with some recent MHD simulations and in situ observations of Cluster spacecraft.