Statistical Evidence for the Existence of Alfv\'enic Turbulence in Solar Coronal Loops

TL;DR

This study provides observational evidence supporting the presence of Alfvénic turbulence in solar coronal loops, which may be crucial for understanding energy dissipation and heating in the solar corona.

Contribution

The paper extends previous research by analyzing a larger sample of coronal loops and establishing a relationship between loop length, wavelength, and wave power enhancement, supporting Alfvénic turbulence.

Findings

Alfvénic perturbations observed with phase speeds of 250-750 km/s.

High-frequency wave-power excess near loop apex depends on loop length and wavelength.

Proportional relationship found between loop length/wavelength ratio and wave power enhancement.

Abstract

Recent observations have demonstrated that waves which are capable of carrying large amounts of energy are ubiquitous throughout the solar corona. However, the question of how this wave energy is dissipated (on which time and length scales) and released into the plasma remains largely unanswered. Both analytic and numerical models have previously shown that Alfv\'enic turbulence may play a key role not only in the generation of the fast solar wind, but in the heating of coronal loops. In an effort to bridge the gap between theory and observations, we expand on a recent study [De Moortel et al., ApJL, 782:L34, 2014] by analyzing thirty-seven clearly isolated coronal loops using data from the Coronal Multi-channel Polarimeter (CoMP) instrument. We observe Alfv\'enic perturbations with phase speeds which range from 250-750 km/s and periods from 140-270 s for the chosen loops. While excesses of high frequency wave-power are observed near the apex of some loops (tentatively supporting the onset of Alfv\'enic turbulence), we show that this excess depends on loop length and the wavelength of the observed oscillations. In deriving a proportional relationship between the loop length/wavelength ratio and the enhanced wave power at the loop apex, and from the analysis of the line-widths associated with these loops, our findings are supportive of the existence of Alfv\'enic turbulence in coronal loops.