Plasma Heating in an Erupting Prominence Detected from Microwave Observations with the Siberian Radioheliograph

A major eruptive flare occurred on 12 January 2022 in the northeast not far behind the solar limb (N32 E116). The eruption produced a fast coronal mass ejection (CME). The rising ejecta was observed by the telescopes in the extreme ultraviolet and by the multi-frequency Siberian Radioheliograph (SRH) in the 5.8 – 11.8 GHz range. We show how the slope of the decrease in the brightness temperature of the rising ejecta, measured from the microwave SRH images, is related to the heat inflow or outflow in its body during rapid expansion with high acceleration and under the assumption that the plasma ionization state changes insignificantly within the measurement interval. We found that the low-temperature plasma component in the erupting prominence underwent heating. Most likely, this was due to the predominance of ohmic heating because i) the polytropic index of expanding plasma expected in this case was closest to the experimentally measured one, and ii) the ohmic dissipation due to electron-proton collisions loses its efficiency during expansion much slower than the other mechanisms of heating or cooling.