NONLINEAR MAGNETIC RECONNECTION WITH COLLISIONLESS DISSIPATION

An analytical model of two-dimensional collisionless reconnection in a n X-type magnetic geometry is presented. The conversion of magnetic en ergy to the kinetic energy of accelerated ions takes place in the vici nity of the neutral line. The structure of this dissipation region and the magnetic energy release rate have been investigated both for line ar and nonlinear regimes of collisionless reconnection. A simple model of global reconnection flow has been constructed, assuming an incompr essible ideal magnetohydrodynamics approximation outside the dissipati on region. The corresponding scaling for the external Mach number (M(e )) is found, which predicts a maximum reconnection rate M(e)=1/2 (R) o ver tilde(m) (-1/2), where (R) over tilde(m) approximate to(L(e)/lambd a(i))(2) much greater than 1 is the effective magnetic Reynolds number for collisionless reconnection (L(e) is the global size of the system and lambda(i) is the ion inertial skin depth). (C) 1995 American Inst itute of Physics.