Nonlinear magnetic reconnection with collisionless dissipation

An analytical model of two-dimensional collisionless reconnection in an X-type magnetic geometry is presented. The conversion of magnetic energy to the kinetic energy of accelerated ions takes place in the vicinity of the neutral line. The structure of this dissipation region and the magnetic energy release rate have been investigated both for linear and nonlinear regimes of collisionless reconnection. A simple model of global reconnection flow has been constructed, assuming an incompressible ideal magnetohydrodynamics approximation outside the dissipation region. The corresponding scaling for the external Mach number (M_e) is found, which predicts a maximum reconnection rate M_e=1/2R̃_m ^−1/2, where R̃_m≊(L_e/λ_i)²≫1 is the effective magnetic Reynolds number for collisionless reconnection (L_e is the global size of the system and λ_i is the ion inertial skin depth).