Spontaneous non-steady magnetic reconnection within the solar environment

TL;DR

This paper uses 2.5D simulations to study spontaneous transition from slow to fast magnetic reconnection in the solar atmosphere, revealing a new mechanism independent of local resistivity enhancements.

Contribution

It identifies a novel mechanism for the transition to fast reconnection, captured only at high resolution, advancing understanding of solar atmospheric phenomena.

Findings

Transition from slow to fast reconnection occurs spontaneously.

The mechanism is independent of local resistivity enhancements.

High-resolution simulations are essential to capture the transition.

Abstract

This work presents a 2.5-dimensional simulation study of the instability of current-sheets located in a medium with a strong density variation along the current layer. The initial force-free configuration is observed to undergo a two-stage evolution consisting of an abrupt regime transition from a slow to a fast reconnection process leading the system to a final chaotic configuration. Yet, the onset of the fast phase is not determined by the presence of any anomalous enhancement in plasma's local resistivity, but rather is the result of a new mechanism discovered in Lapenta (2008)* and captured only when sufficient resolution is present. Hence, the effects of the global resistivity, the global viscosity and the plasma beta on the overall dynamics are considered. This mechanism allowing the transition from slow to fast reconnection provides a simple but effective model of several processes taking place within the solar atmosphere from the high chromosphere up to the low corona. In fact, the understanding of a spontaneous transition to a self-feeding fast reconnection regime as well as its macroscopic evolution is the first and fundamental step to produce realistic models of all those phenomena requiring fast (and high power) triggering events (* Lapenta G. 2008, Phys. Rev. Lett., 100, 235001).