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Energy release during the post main impulsive phase of an eruptive solar flare

Presentation #302.05 in the session Explosive Energy Release Processes in the Solar Corona and Earth’s Magnetosphere I.

Published onOct 20, 2022
Energy release during the post main impulsive phase of an eruptive solar flare

When and where the magnetic field energy is released and converted re- mains an outstanding question in the physics of solar flares. Here we report microwave imaging spectroscopy observations of a C9.4-class eruptive limb flare that occurred on 2017 August 20, using data obtained by the Expanded Owens Valley Solar Array. The flare features four X-ray and microwave pulses imme- diately following the main impulsive phase. For each pulse, both microwave and X-ray imaging suggest that the non-thermal electrons are located in the above-the-loop-top region. Interestingly, the microwave and X-ray flux increase for pulses occurring at later times. Spectral analysis reveals that the sources have either an increasing nonthermal electron density or a hardening spectral index, which is suggestive of a more efficient electron acceleration into the later times of the flare impulsive phase. In addtion, the location of the microwave and X-ray source shows a systematic northward movement, which coincides with the successive brightenings at the flare ribbons. The observations seem to run contradictory to the standard flare scenario in which the flare energy release and electron acceleration diminish quickly after the main impulsive phase. We discuss implications for flare energy release and electron acceleration in relation to the flux rope eruption and the evolution of the flare geometry.

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