# The plasmoid instability in a confined solar flare

## TL;DR

This paper investigates the role of plasmoid instability in confined solar flares, supported by magnetohydrodynamic simulations, suggesting it as a key driver of impulsive phases even without filament eruption.

## Contribution

It introduces the plasmoid instability as a plausible mechanism for impulsive flare phases in confined flares, supported by simulation results and theoretical analysis.

## Key findings

- Plasmoid instability can explain impulsive phases in confined flares.
- Simulations show nonlinear development of plasmoid instability in active regions.
- The mechanism may also apply to eruptive flares with filament eruptions.

## Abstract

Eruptive flares (EFs) are associated with erupting filaments and, in some models, filament eruption drives flare reconnection. Recently, however, observations of a confined flare (CF) have revealed all the hallmarks of an EF (impulsive phase, flare ribbons, etc.) without the filament eruption itself. Therefore, if the filament is not primarily responsible for impulsive flare reconnection, what is? In this Letter, we argue, based on mimimal requirements, that the plasmoid instability is a strong candidate for explaining the impulsive phase in the observed CF. We present magnetohydrodynamic simulation results of the nonlinear development of the plasmoid instability, in a model active region magnetic field geometry, to strengthen our claim. We also discuss how the ideas described in this Letter can be generalised to other situations, including EFs.