Heating in the Solar Atmosphere at a Fin Current Sheet Driven by Magnetic Flux Cancellation

TL;DR

This paper develops nonlinear models for fin current sheets in the solar atmosphere, showing they can extend from the surface and typically release more energy than floating current sheets during magnetic reconnection.

Contribution

It introduces finite-length models for fin current sheets in solar magnetic reconnection, extending previous short-sheet models and enabling energy release calculations.

Findings

Fin current sheets can extend from the solar surface.

Fin sheets generally release more energy than floating sheets.

Models relate current sheet length to source separation and reconnection rate.

Abstract

Magnetic reconnection before flux cancellation in the solar photosphere when two opposite-polarity photospheric magnetic fragments are approaching one another is usually modelled by assuming that a small so-called "floating current sheet" forms about a null point or separator that is situated in the overlying atmosphere. Here instead we consider the reconnection that is initiated as soon as the fragments become close enough that their magnetic fields interact. The resulting current sheet, which we term a "fin sheet" extends up from the null point or separator that is initially located in the solar surface. We develop here nonlinear analyses for finite-length models of both fin and floating current sheets that extend the previous models that were limited to short floating current sheets. These enable the length of the current sheet to be calculated in both cases as functions of the separation distance of the sources and the reconnection rate, as well as the rate of heating. Usually, the fin current sheet liberates more energy than a floating current sheet.