Twin Null-Point-Associated Major Eruptive Three-Ribbon Flares with Unusual Microwave Spectra
Abstract
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.
Keywords
Cite
@article{arxiv.2009.10350,
title = {Twin Null-Point-Associated Major Eruptive Three-Ribbon Flares with Unusual Microwave Spectra},
author = {V. V. Grechnev and N. S. Meshalkina and A. M. Uralov and A. A. Kochanov and S. V. Lesovoi and I. I. Myshyakov and V. I. Kiselev and D. A. Zhdanov and A. T. Altyntsev and M. V. Globa},
journal= {arXiv preprint arXiv:2009.10350},
year = {2020}
}
Comments
23 pages, 9 figures, "This is a pre-print of an article which will be published in Solar Physics"