# Oscillations excited by plasmoids formed during magnetic reconnection in vertical gravitationally stratified current-sheet

## TL;DR

This study uses 2D resistive MHD simulations to analyze plasmoid formation, dynamics, and oscillations during magnetic reconnection in a stratified current sheet, relevant to solar flare processes.

## Contribution

It provides detailed insights into plasmoid oscillations, merging behaviors, and wave generation during magnetic reconnection in a stratified solar-like environment.

## Key findings

- Plasmoids form via tearing mode instability during reconnection.
- Merging of plasmoids induces oscillations with periods of 25-35 seconds.
- Merging processes generate magnetoacoustic waves and complex structures.

## Abstract

Using the FLASH code, which solves the full set of the two-dimensional (2-D) non-ideal (resistive) time-dependent magnetohydrodynamic (MHD) equations, we study processes during the magnetic reconnection in a vertical gravitationally stratified current sheet. We show that during these processes, which correspond to processes in solar flares, plasmoids are formed due to the tearing mode instability of the current sheet. These plasmoids move upwards or downwards along the vertical current sheet, and some of them merge into larger plasmoids. We study the density and temperature structure of these plasmoids and their time evolution in details. We found that during the merging of two plasmoids the resulting larger plasmoid starts to oscillate; in our model with a $\sim 25~\mathrm{s}$ period. On the other hand, the plasmoid moving downwards merges with the underlying flare arcade which also starts to oscillate during this process; in our model with a $\sim 35~\mathrm{s}$ period. It is shown that the merging process of plasmoid with the flare arcade is a complex process as presented by complex density and temperature structures of the oscillating arcade. Moreover, all these processes are associated with magnetoacoustic waves produced by the motion and merging of plasmoids.