Quasi-periodic pulsations in extreme-ultraviolet brightenings

¹ Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
² Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Ringlaan -3- Av. Circulaire, 1180 Brussels, Belgium
³ Astronomy & Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, DIAS Dunsink Observatory, Dublin, D15 XR2R, Ireland
⁴ Solar Physics Laboratory, Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁵ Physics Department, The Catholic University of America, Washington, DC 20064, USA

^⋆ Corresponding author: daye.lim@kuleuven.be

Received: 17 March 2025
Accepted: 20 April 2025

Abstract

Context. Extreme-ultraviolet (EUV) observations have revealed small-scale transient brightenings that may be caused by the same physical mechanisms as larger-scale solar flares. A notable feature of solar and stellar flares is the presence of quasi-periodic pulsations (QPPs), which are a potentially intrinsic characteristic.

Aims. We investigated the properties of QPPs detected in EUV brightenings, which are considered to be small-scale flares, and compared their statistical properties with those observed in solar and stellar flares.

Methods. We extracted integrated light curves of 22 623 EUV brightenings in two quiet Sun regions observed by the Solar Orbiter/Extreme Ultraviolet Imager and identified QPPs in their light curves using Fourier analysis.

Results. Approximately 2.7% of the EUV brightenings exhibited stationary QPPs. The QPP occurrence rate increased with the surface area, lifetime, and peak brightness of the EUV brightenings. The detected QPP periods ranged from approximately 15 to 260 seconds, which is comparable to the periods observed in solar and stellar flares. Consistent with observations of QPPs in solar and stellar flares, no correlation was found between the QPP period and peak brightness. However, unlike the trend observed in solar flares, no correlation was found between the QPP period and the lifetime or length scale.

Conclusions. The presence of QPPs in EUV brightenings supports the interpretation that these events may be small-scale manifestations of flares, and the absence of period scaling with loop length further suggests that standing waves may not be the primary driver of QPPs in these events.