Quasi-periodic acceleration of electrons in the flare on 2012 July 19

Huang, J., Kontar, E. P. , Nakariakov, V. M. and Gao, G. (2016) Quasi-periodic acceleration of electrons in the flare on 2012 July 19. Astrophysical Journal, 831(2), 119. (doi:10.3847/0004-637X/831/2/119)

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Quasi-periodic pulsations (QPPs) of nonthermal emission in an M7.7 class flare on 2012 July 19 are investigated with spatially resolved observations at microwave and HXR bands and with spectral observations at decimetric, metric waves. Microwave emission at 17 GHz of two footpoints, HXR emission at 20–50 keV of the north footpoint and loop top, and type III bursts at 0.7–3 GHz show prominent in-phase oscillations at 270 s. The microwave emission of the loop leg has less pulsation but stronger emission. Through the estimation of plasma density around the loop top from EUV observations, we find that the local plasma frequency would be 1.5 GHz or even higher. Thus, type III bursts at 700 MHz originate above the loop top. Quasi-periodic acceleration or injection of energetic electrons is proposed to dominate these in-phase QPPs of nonthermal emission from footpoints, loop top, and above. In the overlying region, drifting pulsations (DPS) at 200–600 MHz oscillate at a distinct period (200 s). Its global structure drifts toward lower frequency, which is closely related to upward plasmoids observed simultaneously from EUV emission. Hence, nonthermal emission from overlying plasmoids and underlying flaring loops show different oscillating periods. Two individual systems of quasi-periodic acceleration of electrons are proposed to coincide in the bi-direction outflows from the reconnection region.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Kontar, Professor Eduard
Authors: Huang, J., Kontar, E. P., Nakariakov, V. M., and Gao, G.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:IOP Publishing
ISSN (Online):1538-4357
Published Online:03 November 2016
Copyright Holders:Copyright © 2016 The American Astronomical Society
First Published:First published in Astrophysical Journal 831(2): 119
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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