Heating of a plasma sheet in nonequilibrium ionization with nonthermal electrons

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.