Electron Energization in Reconnection Outflows with Kinetic Riemann Simulations

Abstract:

How electrons are heated during magnetic reconnection in the corona has been a basic puzzle for a long time. Here we carry out PIC Riemann simulations to explore electron energization including its dependence on parameters. One-dimensional Riemann simulations, with its simple magnetic geometry, facilitate the study of the reconnection outflow far downstream of x-line in much more detail than is possible with conventional reconnection simulations. We examine the behavior of the electron temperature in this configuration. We find that the electron temperature in the exhaust increases and approaches a constant. Since the heating is independent of the x-line in the Riemann model, these results suggest that electron heating in the exhausts can extend to macroscopic scales in the corona. In runs with guide field, such heating only weakly depends on the proton-to-electron mass ratio used in the simulation. The scaling of the electron temperature increment with the available magnetic energy is discussed and comparisons with conventional reconnection simulations are made.