Very Long-period Pulsations before the Onset of Solar Flares

TL;DR

This paper reports the discovery of very long-period pulsations in the preflare phase of solar flares, observed via soft X-ray emissions, which could serve as precursors for flare prediction and understanding their triggering mechanisms.

Contribution

It introduces the first observation of preflare long-period pulsations (8-30 min) that last for 1-2 hours, suggesting a new potential precursor for solar flare onset.

Findings

Preflare pulsations have periods of 8-30 minutes.

These pulsations last about 1-2 hours before flares.

They may originate from LRC oscillations in plasma loops.

Abstract

Solar flares are the most powerful explosions occurring in the solar system, which may lead to disastrous space weather events and impact various aspects of our Earth. So far, it is still a big challenge in modern astrophysics to understand the origin of solar flares and predict their onset. Based on the analysis of soft X-ray emission observed by the Geostationary Operational Environmental Satellite (GOES), this work reported a new discovery of very long-periodic pulsations occurred in the preflare phase before the onset of solar flares (preflare-VLPs). These pulsations are typically with period of 8 - 30 min and last for about 1 - 2 hours. They are possibly generated from LRC oscillations of plasma loops where electric current dominates the physical process during magnetic energy accumulation in the source region. The preflare-VLP provides an essential information for understanding the triggering mechanism and origin of solar flares, and may help us to response to solar explosions and the corresponding disastrous space weather events as a convenient precursory indicator.