http://arxiv.org/abs/2006.13423
The very long-periodic pulsations during preflare phases (preflare-VLPs) were detected in the full-disk solar soft X-Ray (SXR) flux (see, Tan et al. 2016). They might be regarded as the precursors of solar flares, and could help us to well understand the trigger mechanism of solar flares. In this letter, we report a preflare-VLP event before the onset of an M1.1 circular-ribbon flare on 2015 October 16. It was simultaneously observed in Halpha, SXR, and Extreme ultraviolet (EUV) wavelengths, which were recorded by the NVST, GOES, EVE, and AIA respectively. The preflare-VLP is identified as the repeat and quasi-periodic pulses in light curves during preflare phase, which might be modulated by LRC-circuit oscillation in the current-carrying plasma loop. The quasi-periodicity can be determined from the Fourier power spectrum with Markov chain Monte Carlo (MCMC)-based Bayesian (e.g., Liang et al. 2020), such as ~9.3 minutes. We firstly report a preflare-VLP event in the local Halpha line and EUV wavelength, which could be considered as the precursor of a solar flare. Therefore, it should be useful for the prediction of solar flares, especially for a powerful flare.
D. Li, S. Feng, W. Su, et. al.
Thu, 25 Jun 20
33/78
Comments: 4 pages, 4 figures, accepted by A&A Letters. The abstract was rewritten
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