The Relation between Ion Temperature Anisotropy and Formation of Slow Shocks in Collisionless Magnetic Reconnection

TL;DR

This study uses 2D electromagnetic hybrid simulations to explore how ion temperature anisotropy affects the formation of slow shocks during collisionless magnetic reconnection in low beta plasmas, revealing that anisotropy suppresses shock formation near the neutral point but diminishes with distance.

Contribution

It demonstrates the impact of ion temperature anisotropy on slow shock formation and identifies the spatial regions where shocks are likely to develop during magnetic reconnection.

Findings

Ion temperature anisotropy suppresses slow shock formation near the neutral point.

Shock structures form at distances greater than 115 ion inertial lengths from the neutral point.

Ion temperature anisotropy relaxes with increasing distance from the magnetic neutral point.

Abstract

We perform a two-dimensional simulation by using an electromagnetic hybrid code to study the formation of slow-mode shocks in collisionless magnetic reconnection in low beta plasmas, and we focus on the relation between the formation of slow shocks and the ion temperature anisotropy enhanced at the shock downstream region. It is known that as magnetic reconnection develops, the parallel temperature along the magnetic field becomes large in association with the anisotropic PSBL (plasma sheet boundary layer) ion beams, and this temperature anisotropy has a tendency to suppress the formation of slow shocks. Based on our simulation result, we found that the slow shock formation is suppressed due to the large temperature anisotropy near the X-type region, but the ion temperature anisotropy relaxes with increasing the distance from the magnetic neutral point. As a result, two pairs of current structures, which are the strong evidence of dissipation of magnetic field in slow shocks, are formed at the distance x > 115 ion inertial lengths from the neutral point.