Statistical investigation of solar flares showing quasi-periodicity based on STIX quick-look light curves

Abstract

Context. The emission of radiation associated with the release of energy in solar flares is often modulated according to a quasi-oscillatory pattern. This behavior is known as quasi-periodic pulsation (QPP). In this work, the STIX instrument on board Solar Orbiter was used to study solar flares that show quasi-periodic variations in X-ray emission.Aims. This work aimed to conduct a statistical study of the periods and amplitudes of QPPs observed in quick-look light curves of the STIX instrument.Methods. The quick-look light curves recorded from April 14, 2020 (the beginning of the mission) to the end of March, 2022 were scrutinized. 129 flares with the most distinct pulses were selected, for which the periodicity analysis was carried out using the Lomb-Scargle periodogram and the autocorrelation method. This sample contained mostly weak B- and C-class flares.Results. It was found that 70% of examined flares showed statistically significant oscillations. Longer periods occur less frequently than shorter ones. We also identified a relationship between the period and the duration in which the oscillations were observed.