Letter to the Editor

Flare-induced decay-less transverse oscillations in solar coronal loops^⋆

¹ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: smandal.solar@gmail.com
² School of Earth and Space Sciences, Peking University, Beijing 100871, PR China
³ Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China

Received: 14 June 2021
Accepted: 5 July 2021

Abstract

Evidence of flare-induced, large-amplitude, decay-less transverse oscillations is presented. A system of multithermal coronal loops, as observed with the Atmospheric Imaging Assembly (AIA), exhibit decay-less transverse oscillations after a flare erupts nearby one of the loop footpoints. Measured oscillation periods lie between 4.2 min and 6.9 min wherein the displacement amplitudes range from 0.17 Mm to 1.16 Mm. A motion-magnification technique has been employed to detect the preflare decay-less oscillations. These oscillations have similar periods (between 3.7 min and 5.0 min) similar to the previous ones, but their amplitudes (0.04 Mm to 0.12 Mm) are found to be significantly smaller. No phase difference is found among oscillating threads of a loop when observed through a particular AIA channel or when their multichannel signatures are compared. These features suggest that the occurrence of a flare in this case neither changed the nature of these oscillations (decaying versus decay-less), nor the oscillation periods. The only effect the flare has is to increase the oscillation amplitudes.