What drives decayless kink oscillations in active region coronal loops on the Sun?

TL;DR

This study investigates decayless kink oscillations in active region coronal loops using high-resolution solar observations, finding no clear driver and suggesting the need for further research into their origins.

Contribution

The paper provides detailed observational analysis showing decayless oscillations occur without the typical drivers like supergranular flows or transient events.

Findings

Decayless oscillations are more resolved in higher-resolution data.

Oscillations occur even when loops are rooted in sunspots.

Common proposed drivers are not supported by the observations.

Abstract

We study here the phenomena of decayless kink oscillations in a system of active region (AR) coronal loops. Using high resolution observations from two different instruments, namely the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we follow these AR loops for an hour each on three consecutive days. Our results show significantly more resolved decayless waves in the higher-resolution EUI data compared with the AIA data. Furthermore, the same system of loops exhibits many of these decayless oscillations on Day-2, while on Day-3, we detect very few oscillations and on Day-1, we find none at all. Analysis of photospheric magnetic field data reveals that at most times, these loops were rooted in sunspots, where supergranular flows are generally absent. This suggests that supergranular flows, which are often invoked as drivers of decayless waves, are not necessarily driving such oscillations in our observations. Similarly, our findings also cast doubt on other possible drivers of these waves, such as a transient driver or mode conversion of longitudinal waves near the loop footpoints. In conclusion, through our analysis we find that none of the commonly suspected sources proposed to drive decayless oscillations in active region loops seems to be operating in this event and hence, the search for that elusive wave driver needs to continue.