Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare

Abstract

Solar flares are sudden energy release events in the solar corona, resulting from magnetic reconnection, that accelerates particles and heats the ambient plasma. During a flare, there are often multiple, temporally and spatially separated individual energy release episodes that can be difficult to resolve depending on the observing instrument. We present multi-wavelength imaging and spectroscopy observations of multiple electron acceleration episodes during a GOES B1.7-class two-ribbon flare on 2012 February 25, observed simultaneously with the Karl G. Jansky Very Large Array (VLA) at 1--2 GHz, the Reuven Ramatay High Energy Solar Spectroscopic Imager (RHESSI) in X-rays, and the Solar Dynamics Observatory in extreme ultraviolet (EUV). During the initial phase of the flare, five radio bursts were observed. A nonthermal X-ray source was seen co-temporal, but not co-spatial, with the first three radio bursts. Their radio spectra are interpreted as optically thick gyrosynchrotron emission. By fitting the radio spectra with a gyrosynchrotron model, we derive the magnetic field strength and nonthermal electron spectral parameters in each acceleration episode. Notably, the nonthermal parameters derived from X-rays differ considerably from the nonthermal parameters inferred from the radio. The observations are indicative of multiple, co-temporal acceleration episodes during the impulsive phase of a solar microflare. The X-ray and radio burst sources likely originate from separate electron distributions in different magnetic loops.

16 pages, 12 figures

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Cited by in corpus (6)

• STIX X-ray microflare observations during the Solar Orbiter commissioning phase
• Radio Spectral Imaging of an M8.4 Eruptive Solar Flare: Possible Evidence of a Termination Shock
• Detection of weak ubiquitous impulsive nonthermal emissions from the solar corona
• Multiple electron acceleration instances during a series of solar microflares observed simultaneously at X-rays and microwaves
• Noise in Maps of the Sun at Radio Wavelengths II: Solar Use Cases
• Non-thermal electron energization during the impulsive phase of an X9.3 flare revealed by Insight-HXMT