Effect of electron dynamics on collisionless reconnection in two‐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 Bz. Two‐dimensional (x, z) simulations in which both electrons and ions are treated as particles demonstrate that, for the case of thin current sheets (Ri/ λ ∼ 1, where Ri is the ion Larmor radius based on the lobe field and λ is the current sheet half thickness) and with weakly chaotic electron orbits, the ion tearing mode is indeed stabilized under the mild condition that kρe ≲ 1, where ρe is the electron Larmor radius in the Bz field.