A Statistical Study of Short-period Decayless Oscillations of Coronal Loops in an Active Region

TL;DR

This study statistically analyzes short-period decayless transverse oscillations in coronal loops using high-resolution Solar Orbiter data, revealing their properties, dependence on loop length, and implications for coronal heating.

Contribution

It provides the first comprehensive statistical analysis of short-period decayless coronal loop oscillations, including measurements of periods, loop lengths, kink speeds, magnetic fields, and energy flux.

Findings

Oscillations have periods from 11 to 185 seconds with a median of 40 seconds.

Oscillatory periods strongly depend on loop lengths, indicating standing kink-mode waves.

Energy flux from these oscillations is insufficient for coronal heating.

Abstract

Coronal loop oscillations are common phenomena in the solar corona, which are often classified as decaying and decayless oscillations. Using the high-resolution observation measured by the Extreme Ultraviolet Imager (EUI) onboard the Solar Orbiter, we statistical investigate small-scale transverse oscillations with short periods (<200 s) of coronal loops in an active region, i.e., NOAA 12965. A total of 111 coronal loops are identified in EUI 174 A images, and they all reveal transverse oscillations without any significant decaying, regarding as decayless oscillations. Oscillatory periods are measured from about 11 s to 185 s, with a median period of 40 s. Thus, they are also termed as short-period oscillations. The corresponding loop lengths are measured from about 10.5 Mm to 30.2 Mm, and a strong dependence of oscillatory periods on loop lengths is established, indicating that the short-period oscillations are standing kink-mode waves in nature. Based on the coronal seismology, kink speeds are measured to about 330-1910 km/s, and magnetic field strengths in coronal loops are estimated to about 4.1-25.2 G, while the energy flux carried by decayless kink oscillations lies in the range from roughly 7 W m^(-2) to 9220 W m^(-2). Our estimations suggest that the wave energy carried by short-period decayless kink oscillations can not support the coronal heating in the active region.