Energy Partitions and Evolution in a Purely Thermal Solar Flare

TL;DR

This study analyzes a purely thermal solar flare using microwave emissions to measure magnetic, thermal, and energy evolution, revealing magnetic energy decreases with incomplete thermal compensation and energy recovery post-flare.

Contribution

It demonstrates the use of thermal gyro emission to precisely measure magnetic fields and track energy evolution in a thermal solar flare, a novel approach in flare analysis.

Findings

Magnetic energy density declines during flare rise phase.

Thermal energy increases but does not fully compensate magnetic energy loss.

Magnetic and thermal energies nearly recover after the flare.

Abstract

This paper presents a solely thermal flare, which we detected in the microwave range from the thermal gyro- and free-free emission it produced. An advantage of analyzing thermal gyro emission is its unique ability to precisely yield the magnetic field in the radiating volume. When combined with observationally-deduced plasma density and temperature, these magnetic field measurements offer a straightforward way of tracking evolution of the magnetic and thermal energies in the flare. For the event described here, the magnetic energy density in the radio-emitting volume declines over the flare rise phase, then stays roughly constant during the extended peak phase, but recovers to the original level over the decay phase. At the stage where the magnetic energy density decreases, the thermal energy density increases; however, this increase is insufficient, by roughly an order of magnitude, to compensate for the magnetic energy decrease. When the magnetic energy release is over, the source parameters come back to nearly their original values. We discuss possible scenarios to explain this behavior.