A test electron model for the study of three dimensional magnetic reconnection effects

Understanding the mechanisms that enable the conversion of the explosive release of magnetic energy into the electron energization that is experimentally observed in space and laboratory plasmas represents a long-standing question in the study of magnetic reconnection.We present a test particle model able to follow the dynamics of the electron guiding centers in the presence of the electromagnetic fields characterizing a non-steady-state, three-dimensional magnetohydrodynamic (3D-MHD) description of magnetic reconnection. The resulting electron equations, based on a relativistic Hamiltonian formulation of the particle dynamics, have been implemented in a code that evolves the spatial position and the velocity of the electrons according to the fields obtained by the numerical solutions of a two-fluid reconnection model. By the calculation of the electron distribution function in the phase space, the electron kinetic moments can be obtained with a δfδf technique particularly suitable during the early stages of the reconnection process, which can be replaced by a full-ff approach in the nonlinear reconnection phase. Thanks to its capability to reproduce the electron response in a quite realistic reconnection configuration, this numerical tool represents a new instrument for the investigation of the nonlinear electron dynamics in particularly complex reconnection regions, such as those characterized by magnetic field line stochasticity.