Electron response to collisionless magnetic reconnection

A gyrokinetic test particle code, based on a relativistic Hamiltonian guiding-center formulation, has been developed in order to investigate the behavior of an electron population during a collisionless magnetic reconnection event. The reconstruction of the electron distribution function allows for a detailed comparison between the fluid quantities and the corresponding kinetic moments. Numerical simulations show that, during the linear stage, the growth rates are in agreement, the kinetic density evolves according to the fluid vorticity, and the parallel kinetic temperature remains uniformly distributed in the spatial domain. Only during the nonlinear stage, hotter regions are observed in the magnetic island. The rise in the temperature is associated with a deformation of the electron distribution function, which, however, does not present highly energetic or relativistic tails. This result provides a preliminary indication to which phase of the process the fluid reconnection model assumption of isothermal electrons is valid.