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

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.

Accepted for publication in A&A Letters. Event movies can be downloaded from https://drive.google.com/drive/folders/1IFH17oBwJuz2U5zR4Ds_Y4oU5ZQCaVbR?usp=sharing

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• Traveling kink oscillations of coronal loops launched by a solar flare
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• A Statistical Investigation of Decayless Oscillations in Small-scale Coronal Loops Observed by Solar Orbiter/EUI
• 30-min Decayless Kink Oscillations in a Very Long Bundle of Solar Coronal Plasma Loops
• Signatures of dynamic fibrils at the coronal base: Observations from Solar Orbiter/EUI
• Decayless oscillations in 3D coronal loops excited by a power-law driver
• Evolution of dynamic fibrils from the cooler chromosphere to the hotter corona
• Characteristics and Energy Flux Distributions of Decayless Transverse Oscillations Depending on Coronal Regions
• Coronal kink oscillations and photospheric driving: combining SolO/EUI and SST/CRISP high-resolution observations
• Undersampling effects on observed periods of coronal oscillations
• Microwave response to kink oscillations of a plasma slab
• Anomalous cross-field motions of solar coronal loops
• Long-lived coronal loops in solar active regions
• Data-driven Radiative Magnetohydrodynamics Simulations with the MURaM Code: Coronal Heating and Dynamics in an Emerging Active Region
• Active region upflows in various coronal structures and their coupling to the lower atmosphere
• Polarization of decayless kink oscillations in a 3D MHD coronal loop model