Quasi-periodic pulsations of gamma-ray emissions from a solar flare on 2017 September 06

TL;DR

This study analyzes quasi-periodic pulsations in gamma-ray, X-ray, and radio emissions from a powerful solar flare, revealing periodicities linked to particle acceleration and magnetic reconnection, with implications for stellar flare understanding.

Contribution

It identifies and characterizes QPPs in a major solar flare across multiple wavelengths, suggesting mechanisms like magnetic reconnection or MHD oscillations as causes.

Findings

QPP periods are 24-30 s in HXR and microwave channels.

QPP period is ~20 s in gamma-ray emissions.

QPPs are associated with nonthermal particle acceleration.

Abstract

We investigate quasi-periodic pulsations (QPPs) of high-energy nonthermal emissions from an X9.3 flare (SOL2017-Sep-06T11:53), the most powerful flare since the beginning of solar cycle 24. The QPPs are identified as a series of regular and repeating peaks in the light curves in the gamma- and hard X-ray (HXR) channels recorded by the Konus-Wind, as well as the radio and microwave fluxes measured by the CALLISTO radio spectrograph during the impulsive phase. The periods are determined from the global wavelet and Fourier power spectra, as 24-30 s in the HXR and microwave channels which are associated with nonthermal electrons, and ~20 s in the gamma-ray band related to nonthermal ions. Both nonthermal electrons and ions may be accelerated by repetitive magnetic reconnection during the impulsive phase. However, we could not rule out other mechanisms such as the MHD oscillation in a sausage mode. The QPP detected in this study is useful for understanding the particle acceleration and dynamic process in solar flares and also bridging the gap between stellar and solar flares since the energy realm of the X9.3 solar flare is almost compared with a typical stellar flare.