2.5-D MHD Simulation of the Formation and Evolution of Plasmoids in Coronal Current Sheets

TL;DR

This paper uses 2.5-D MHD simulations to demonstrate how external velocity pulses can trigger magnetic reconnection and plasmoid formation in solar coronal current sheets, matching observed plasma properties.

Contribution

It shows that a single velocity pulse can initiate reconnection and plasmoid formation without localized resistivity enhancement in the solar corona.

Findings

Plasmoids have velocities of 105-303 km/s.

Average plasmoid temperature is 8 MK.

Plasmoid density is twice the background density.

Abstract

In the present paper, using MPI-AMRVAC, we perform a 2.5-D numerical MHD simulation of the dynamics and associated thermodynamical evolution of an initially force-free Harris current sheet subjected to an external velocity perturbation under the condition of uniform resistivity. The amplitude of the magnetic field is taken to be 10 Gauss, typical of the solar corona. We impose a Gaussian velocity pulse across this current sheet mimicking the interaction of fast magnetoacoustic waves with a current sheet in corona. This leads to a variety of dynamics and plasma processes in the current sheet, which is initially quasi-static. The initial pulse interacts with the current sheet and splits into a pair of counter-propagating wavefronts, which forms a rarefied region and leads to inflow and a thinning of the current sheet. The thinning results in Petschek-type magnetic reconnection followed by tearing instability and plasmoid formation. The reconnection outflows containing outward-moving plasmoids have accelerated motions with velocities ranging from 105-303 km/s. The average temperature and density of the plasmoids are found to be 8 MK and twice the background density of the solar corona, respectively. These estimates of velocity, temperature and density of plasmoids are similar to values reported from various solar coronal observations. Therefore, we infer that the external triggering of a quasi-static current sheet by a single velocity pulse is capable of initiating magnetic reconnection and plasmoid formation in the absence of a localized enhancement of resistivity in the solar corona.