Collapse of the neutral current sheet and reconnection at micro-scales

TL;DR

This paper investigates micro-scale magnetic reconnection physics, demonstrating a collapse process of the neutral current sheet that leads to rapid reconnection facilitated by electron inertia and Hall currents, supported by analytical and numerical methods.

Contribution

It introduces a new collapse mechanism of the neutral current sheet at micro-scales, combining analytical and numerical solutions to reveal how electron inertia and Hall effects enable fast reconnection.

Findings

Collapse triggers formation of intense sub-sheets and X-points.

Reconnection rate is independent of viscosity.

Maximum current is limited even in space plasmas with rare collisions.

Abstract

Reconnection physics at micro-scales is investigated in an electron magnetohydrodynamics frame. A new process of collapse of the neutral current sheet is demonstrated by means of analytical and numerical solutions. It shows how at scales smaller than ion inertia length a compression of the sheet triggers an explosive evolution of current perturbation. Collapse results in the formation of a intense sub-sheet and then an X-point structure embedded into the equilibrium sheet. Hall currents associated with this structure support high reconnection rates. Nonlinear static solution at scales of the electron skin reveals that electron inertia and small viscosity provide an efficient mechanism of field lines breaking. The reconnection rate does not depend on the actual value of viscosity, while the maximum current is found to be restricted even for space plasmas with extremely rare collisions. The results obtained are verified by a two-fluid large-scale numerical simulation.