EFFECT OF ELECTRON DYNAMICS ON COLLISIONLESS RECONNECTION IN 2-DIMENSIONAL MAGNETOTAIL EQUILIBRIA

Analytic theory has yielded contradictory predictions regarding the stabilizing role of electron dynamics on the collisionless tearing instability in a field-reversal region with finite normal magnetic field component B(z). Two-dimensional (x, z) simulations in which both electrons and ions are treated as particles demonstrate that, for the case of thin current sheets (R(i)/lambda approximately 1, where R(i) is the ion Larmor radius based on the lobe field and lambda is the current sheet half thickness) and with weakly chaotic electron orbits, the ion tearing mode is indeed stabilized under the mild condition that krho(e) less-than-or-equal-to 1, where rho(e) is the electron Larmor radius in the B(z) field.