A simple model of chromospheric evaporation and condensation driven conductively in a solar flare

TL;DR

This paper presents an analytic and numerical model of chromospheric evaporation and condensation driven by thermal conduction during solar flares, providing predictive relations for flow velocities based on coronal parameters.

Contribution

It introduces a simplified yet accurate analytic model for predicting evaporation and condensation flows in solar flares, validated by numerical simulations and applicable to coronal reconnection studies.

Findings

Maximum evaporation velocity approximated by $v_e\simeq0.38(F/\rho_{co,0})^{1/3}$

Relations fit well with realistic transition region models

Provides an efficient method for simulating flare-related flows

Abstract

Magnetic energy released in the corona by solar flares reaches the chromosphere where it drives characteristic upflows and downflows known as evaporation and condensation. These flows are studied here for the case where energy is transported to the chromosphere by thermal conduction. An analytic model is used to develop relations by which the density and velocity of each flow can be predicted from coronal parameters including the flare's energy flux $F$. These relations are explored and refined using a series of numerical investigations in which the transition region is represented by a simplified density jump. The maximum evaporation velocity, for example, is well approximated by $v_e\simeq0.38(F/\rho_{co,0})^{1/3}$, where $\rho_{co,0}$ is the mass density of the pre-flare corona. This and the other relations are found to fit simulations using more realistic models of the transition region both performed in this work, and taken from a variety of previously published investigations. These relations offer a novel and efficient means of simulating coronal reconnection without neglecting entirely the effects of evaporation.