Energy Partitions and Evolution in a Purely Thermal Solar 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 radioemitting 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.

Incoherent Solar Radio Emission

“…Gyrosynchrotron emission can be produced by electrons with either a non-thermal or a thermal distribution; in the latter case (e.g., Gary and Hurford, 1989 and for more recent examples see Fleishman et al, 2015;Wang et al, 2017) they could be electrons heated due to the flare. Usually the emission is first computed for a single electron radiating in cold plasma (e.g., Ramaty, 1969, the "parent" of all modeling papers), while for the thermal case, Gershman (1960) considered small fluctuations in the thermal equilibrium of a magnetized plasma described by the linearized Vlasov equation.…”

Can Substorm Particle Acceleration Be Applied to Solar Flares?

“…The effective heating in the trap could also render it a possible mechanism for flares that show prolonged heating before the impulsive phase (e.g., Veronig et al 2002;Battaglia et al 2014) or for a long time during the post-flare phase (e.g., Kuhar et al 2017), which is apparently without a significant acceleration. It could also be a mechanism for flares that appear entirely thermal (e.g., Fleishman et al 2015). …”

A new class of discontinuous solar wind solutions

“…The values of this relative total energy density difference are given in Table 1, accordingly. It is interesting to note that ET ot for both slow and fast solar wind patterns is by several orders of magnitude smaller than the ammount of total energy released by any standard flare event (e.g., Fleishman et al 2015;Ellison 1963), even taking into account the radial expansion in the upward direction. This fact makes the scenarios described here easily sustainable by any reconnection type explosive event or their combinations in the solar corona.…”