Interaction of reflected ions with the firehose marginally stable current sheet: Implications for plasma sheet convection

The firehose marginally stable current sheet, which may model the flow away from the distant reconnection neutral line, assumes that the accelerated particles escape and never return to re‐encounter the current region. This assumption fails on the earthward side where the accelerated ions mirror in the geomagnetic dipole field and return to the current sheet at distances up to about 30 R E down the tail. Two‐dimensional particle simulations are used to demonstrate that the reflected ions drive a “shock‐like” structure in which the incoming flow is decelerated and the B z field is highly compressed. These effects are similar to those produced by adiabatic choking of steady convection. Possible implications of this interaction for the dynamics of the tail are considered.