Quasi-periodic pulsations in solar and stellar flares

Abstract

Light curves of thermal and non-thermal emission associated with solar flares usually contain statistically significant quasi-periodic pulsations (QPP). Typical periods range from a fraction of a second to several tens of minutes. Physical mechanisms responsible for QPP can be attributed to three main, while non-exclusive, groups: modulation of the emitting plasma parameters and kinematics of non-thermal electrons by coronal magnetohydrodynamic oscillations, spontaneous periodic magnetic reconnection, and magnetic reconnection periodically induced by magnetohydrodynamic oscillations. Similar QPP are also detected in stellar flares, including those hosted by Sun-like stars. Recently, a number of stellar flare QPP events were detected in white light with Kepler. In several cases, the characteristic time signatures of stellar flare QPP are very similar to those detected in solar flares, suggesting that they may be created by the same mechanisms. This report summarises the invited review talk given by V.M. Nakariakov at the workshop “Superflares on solar-type stars and solar flares, and their impacts on exoplanets and the Earth” at Kyoto University in March 2016.