Twin Null-Point-Associated Major Eruptive Three-Ribbon Flares with Unusual Microwave Spectra

Autor: S. V. Lesovoi, D. A. Zhdanov, A. A. Kochanov, M. V. Globa, N. S. Meshalkina, V. V. Grechnev, I. I. Myshyakov, A. T. Altyntsev, V. I. Kiselev, A. M. Uralov
Rok vydání: 2020
Předmět:
Zdroj: Solar Physics. 295
ISSN: 1573-093X
0038-0938
Popis: On 23 July 2016 after 05:00\,UTC, the first 48-antenna stage of the Siberian Radioheliograph detected two flares of M7.6 and M5.5 GOES importance that occurred within half an hour in the same active region. Their multi-instrument analysis reveals the following. The microwave spectra were flattened at low frequencies and the spectrum of the stronger burst had a lower turnover frequency. Each flare was eruptive, emitted hard X-rays and gamma-rays exceeding 800\,keV, and had a rare three-ribbon configuration. An extended hard X-ray source associated with a longest middle ribbon was observed in the second flare. The unusual properties of the microwave spectra are accounted for by a distributed multi-loop system in an asymmetric magnetic configuration that our modeling confirms. Microwave images did not to resolve compact configurations in these flares that may also be revealed incompletely in hard X-ray images because of their limited dynamic range. Being apparently simple and compact, non-thermal sources corresponded to the structures observed in the extreme ultraviolet. In the scenario proposed for two successive three-ribbon eruptive flares in a configuration with a coronal-null region, the first eruption causes a flare and facilitates the second eruption that also results in a flare.
Comment: 23 pages, 9 figures, "This is a pre-print of an article which will be published in Solar Physics"
Databáze: OpenAIRE
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