Heating of a plasma sheet in nonequilibrium ionization with nonthermal electrons

TL;DR

This study models plasma sheet heating during a solar eruption, highlighting the role of nonthermal electrons and nonequilibrium ionization, with impulsive heating exceeding 20 MK and suprathermal electrons being significant.

Contribution

It introduces time-dependent ionization models incorporating non-Maxwellian electron distributions to analyze plasma heating in solar eruptions.

Findings

Impulsive heating temperature exceeds 20 MK.

Low kappa values indicate significant suprathermal electrons.

Impulsive heating accounts for the majority of energy input.

Abstract

A flux rope eruption on September 10, 2017 provides unique observations of the plasma sheet beneath the rising flux rope. The plasma sheet is likely in a nonequilibrium state in terms of both ionization and the electron distribution function. We trace the evolution of a blob in the plasma sheet using observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. We investigate the heating of plasma sheet material in the presence of non-Maxwellian electron distributions and nonequilibrium ionization. Our models compute time-dependent ion fractions, incorporating impulsive heating to various peak temperatures, continuous heating rates, and kappa values that represent the non-Maxwellian distribution. The statistically preferred models constrain the effective impulsive heating temperature to above 20~MK. High-temperature solutions are permitted only for very low kappa values, indicating that suprathermal electrons play a significant role. Impulsive heating dominates the energy budget, with continuous heating contributing approximately 6%-50% of the initial impulsive energy input.