Connecting theory of plasmoid-modulated reconnection to observations of solar flares

TL;DR

This paper links theoretical models of plasmoid formation in solar flare reconnection to actual observations, revealing that plasmoids may form earlier than current theories predict, which could challenge existing models.

Contribution

It applies theoretical scalings of current sheet aspect ratios to observed solar flares, providing new insights into plasmoid formation timing.

Findings

Observed plasmoid formation corresponds to $ ext{α}$ values of 0.27 to 0.31.

Plasmoids may form before reaching the critical aspect ratio predicted by theory.

The results challenge the current theoretical understanding of plasmoid onset.

Abstract

The short timescale of the solar flare reconnection process has long proved to be a puzzle. Recent studies suggest the importance of the formation of plasmoids in the reconnecting current sheet, with quantifying the aspect ratio of the width to length of the current sheet in terms of a negative power $\alpha$ of the Lundquist number, i.e. $S^{-\alpha}$, being key to understanding the onset of plasmoids formation. In this paper we make the first application of theoretical scalings for this aspect ratio to observed flares to evaluate how plasmoid formation may connect with observations. We find that for three different flares showing plasmoids a range of $\alpha$ values of $\alpha= 0.27$ to $0.31$. The values in this small range implies that plasmoids may be forming before the theoretically predicted critical aspect ratio ($\alpha=1/3$) has been reached, potentially presenting a challenge for the theoretical models.