Study of Type III Solar Radio Bursts in Nanoflares

The heating mechanisms responsible for the million-degree solar corona remain one of the most intriguing problems in space science. It is widely agreed, that the ubiquitous presence of reconnection events and the associated impulsive heating (nanoflares) are a strong candidate in solving this problem [Klimchuk J.A., 2015 and references therein].

Whether nanoflares accelerate energetic particles like full-sized flares is unknown. The lack of strong emission in hard X-rays suggests that the quantity of highly energetic particles is small. There could, however, be large numbers of mildly energetic particles (~ 10 keV). We investigate such particles by searching for the type III radio bursts that they may produce. If energetic electron beams propagating along magnetic field lines generate a bump-on-tail instability, they will produce Langmuir waves, which can then interact with other particles and waves to give rise to emission at the local plasma frequency and its first harmonic. Type III bursts are characteristically known to exhibit high frequency drifts as the beam propagates through a density gradient. The time-lag technique that was developed to study subtle delays in light curves from different EUV channels [Viall & Klimchuk 2012] can also be used to detect subtle delays at different radio frequencies. We have modeled the expected radio emission from nanoflares, which we used to test and calibrate the technique. We are applying the technique to actual radio observations from VLA (Very Large Array), MWA (Murchison Widefield Array) and seeking data from LOFAR (Low-Frequency Array) as well. We also plan to use data from the PSP (Parker Solar Probe) to look for similar reconnection signatures in the Solar Wind. Our goal is to determine whether nanoflares accelerate energetic particles and to determine their properties. The results will have important implications for both the particle acceleration and reconnection physics.