The onset of Impulsive Bursty reconnection at a two-dimensional current layer

TL;DR

This paper investigates impulsive bursty magnetic reconnection in a 2D current layer, revealing a two-phase process with energy mainly converting into plasma internal energy, relevant for solar phenomena.

Contribution

It provides a detailed analysis of impulsive bursty reconnection dynamics and energy conversion in a 2D current layer, offering insights for solar physics and future 3D studies.

Findings

Transient phase disperses current and converts energy mainly into internal energy.

Impulsive bursty reconnection occurs with stochastic current buildup and dissipation.

Greater magnetic energy is converted during the quasi-steady phase than initial transient.

Abstract

The sudden reconnection of a non-force free 2D current layer, embedded in a low-beta plasma, triggered by the onset of an anomalous resistivity, is studied in detail. The resulting behaviour consists of two main phases. Firstly, a transient reconnection phase, in which the current in the layer is rapidly dispersed and some flux is reconnected. This dispersal of current launches a family of small amplitude magnetic and plasma perturbations, which propagate away from the null at the local fast and slow magnetosonic speeds. The vast majority of the magnetic energy released in this phase goes into internal energy of the plasma, and only a tiny amount is converted into kinetic energy. In the wake of the outwards propagating pulses, an imbalance of Lorentz and pressure forces creates a stagnation flow which drives a regime of impulsive bursty reconnection, in which fast reconnection is turned on and off in a turbulent manner as the current density exceeds and falls below a critical value. During this phase, the null current density is continuously built up above a certain critical level, then dissipated very rapidly, and built up again, in a stochastic manner. Interestingly, the magnetic energy converted during this quasi-steady phase is greater than that converted during the initial transient reconnection phase. Again essentially all the energy converted during this phase goes directly to internal energy. These results are of potential importance for solar flares and coronal heating, and set a conceptually important reference for future 3D studies.