Revealing ubiquitous weak kink oscillations with fractional anisotropy video motion magnification

Abstract Kink oscillations are transverse displacement fluctuations of coronal loops caused by perturbations, with their phase speed directly related to magnetic field strength, making them a vital tool for diagnosing coronal plasma conditions. In this study, we employ the fractional anisotropy (FA)-based video motion amplification (FA-VMM) technique, combined with the damped harmonic oscillator model and simple harmonic oscillator model, to systematically analyse the small-amplitude oscillations in three sets of coronal loops (one in a flaring active region and two in quiescent active regions) observed in the SDO/AIA 171 Å band. After 20× magnification and model fitting, we find that coronal loops in the steady state generally exhibit intrinsic decayless oscillations, with parameter variations probably reflecting differences in loop properties. Crucially, for the flare-perturbed active-region coronal loop, we document a complete oscillation state transition: the flare-induced disturbance drives a large-amplitude decaying oscillation while the period remained stable throughout; subsequently, the system recovers to its initial decayless state. These findings provide detailed observational evidence for understanding the elasticity of coronal loops and their dynamic response to transient perturbations. This article is part of the theme issue ‘Transferable mechanisms in the oscillatory processes of solar and stellar flares'.