Exploring Plasma Heating in the Current Sheet Region in a Three-dimensional Coronal Mass Ejection Simulation

Abstract

We simulate a coronal mass ejection (CME) using a three-dimensional magnetohydrodynamic (MHD) code that includes coronal heating, thermal conduction, and radiative cooling in the energy equation. The magnetic flux distribution at 1 R s is produced by a localized subsurface dipole superimposed on a global dipole field, mimicking the presence of an active region within the global corona. Transverse electric fields are applied near the polarity inversion line to introduce a transverse magnetic field, followed by the imposition of a converging flow to form and destabilize a flux rope, producing an eruption. We examine the quantities responsible for plasma heating and cooling during the eruption, including thermal conduction, radiation, adiabatic effects, coronal heating, and ohmic heating. We find that ohmic heating is an important contributor to hot temperatures in the current sheet region early in the eruption, but in the late phase adiabatic compression plays an important role in heating the plasma there. Thermal conduction also plays an important role in the transport of thermal energy away from the current sheet region throughout the reconnection process, producing a "thermal halo" and widening the region of high temperatures. We simulate emission from solar telescopes for this eruption and find that there is evidence for emission from heated plasma above the flare loops late in the eruption, when the adiabatic heating is the dominant heating term. These results provide an explanation for hot supra-arcade plasma sheets that are often observed in X-rays and extreme ultraviolet wavelengths during the decay phase of large flares.

Plasma Heating Induced by Tadpole-like Downflows in the Flaring Solar Corona

“…It is also possible that the significant heating results from a strong compression during the collisions. 16 , 17 Thermal conduction could then rapidly spread the heating to the rest of the loops. If the plasma is heated to a temperature of >20 MK, the emission from all Fe-dominated AIA channels should decrease because these channels are generally insensitive to such a high temperature.…”

The Triple-layered Leading Edge of Solar Coronal Mass Ejections

“…Numerical experiments have been performed extensively to study the eruption process of CMEs, including their triggering mechanism (Forbes 1990), the reconnecting current sheet (Reeves et al 2019), the large-scale evolution (Roussev et al 2012;Jiang et al 2018) and the associated coronal EUV disturbances (Downs et al 2012). In earlier numerical studies preceding modern CME simulations, evolutions of cylindrical straight MFRs have been simulated as well (Baty 2001; Bareford et al 2010).…”

Constraining the CME Core Heating and Energy Budget with SOHO/UVCS

“…MAS models the global solar atmosphere from the top of the chromosphere to Earth and beyond, and it has been used extensively to study coronal structure (Mikić et al 1999;Linker et al 1999;Lionello et al 2009b;Downs et al 2013;Mikić et al 2018), coronal dynamics (Lionello et al 2005(Lionello et al , 2006Linker et al 2011) and CMEs (Linker et al 2003;Lionello et al 2013;Török et al 2018;Reeves et al 2010Reeves et al , 2019. MAS solves the resistive, thermodynamic MHD equations in spherical coordinates (r, θ, φ) on structured nonuniform meshes.…”

“…This can be done if the realistic simulation of a CME exhibits physical conditions similar to that of the observed 1999 CME. Reeves et al (2019) thoroughly describes the global behavior and energetics of the CME simulation that we use. Within this CME, we extract an exemplary parcel of plasma and monitor its characteristics as we follow its evolution.…”