Polarization of decayless kink oscillations in a 3D MHD coronal loop model

¹ Max Planck Institute for Solar System Research Justus-von-Liebig-Weg 3 37077 Göttingen, Germany
² The University of Graz Universitätspl. 3 8010 Graz, Austria
³ Institut für Sonnenphysik (KIS) Georges-Köhler-Allee 401a 79110 Freiburg, Germany

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 21 November 2025
Accepted: 6 January 2026

Abstract

Decayless kink oscillations are frequently observed in solar coronal loops and are considered potential contributors to coronal heating. Despite the ubiquity of this wave phenomenon, its driving mechanism remains unclear. Studies to derive the polarization state of these oscillations, which would be a key to identifying the drivers, have been limited by observational constraints. We analyzed a 3D magnetohydrodynamic simulation of coronal loops using the code MURaM. Synthetic extreme-ultraviolet emission maps, combined with velocity diagnostics, were used to identify and characterize transverse wave motions in the simulated loop structures. This is the first demonstration of decayless kink waves that emerge self-consistently in a 3D magnetohydrodynamic loop-in-a-box model. The simulation produces persistent, low-amplitude, decayless kink oscillations that closely match observed properties. These oscillations arise spontaneously, without any imposed periodic driver, and are clearly linearly polarized. The oscillation planes are not aligned with the principal axes. The observed coherence of the linear polarization with the oscillation cycles favors a self-sustained or quasi-steady-type wave driver over a stochastic or broadband source.