Heating of a Plasma Sheet in Nonequilibrium Ionization with Nonthermal Electrons

Abstract A flux rope eruption on 2017 September 10 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 on board 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 κ 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 κ 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.