Coronal Fourier power spectra: implications for coronal seismology and coronal heating

TL;DR

This study analyzes solar coronal regions using Fourier power spectra, revealing a power-law distribution at low frequencies and Gaussian features, challenging previous assumptions and impacting coronal seismology and heating models.

Contribution

It demonstrates that coronal Fourier spectra are characterized by a power law plus Gaussian component, providing new insights into coronal dynamics and heating mechanisms.

Findings

Fourier spectra follow a power law at low frequencies

Spectra include a Gaussian-shaped contribution varying by region

Implications for automated oscillation detection and coronal heating models

Abstract

The dynamics of regions of the solar corona are investigated using Atmospheric Imaging Assembly (AIA) 171\AA\ and 193\AA\ data. The coronal emission from the quiet Sun, coronal loop footprints, coronal moss, and from above a sunspot is studied. It is shown that the mean Fourier power spectra in these regions can be described by a power law at lower frequencies that tails to flat spectrum at higher frequencies, plus a Gaussian-shaped contribution that varies depending on the region studied. This Fourier spectral shape is in contrast to the commonly-held assumption that coronal time-series are well described by the sum of a long time-scale background trend plus Gaussian-distributed noise, with some specific locations also showing an oscillatory signal. The implications of this discovery to the field of coronal seismology and the automated detections of oscillations are discussed. The power law contribution to the shape of the Fourier power spectrum is interpreted as being due to the summation of a distribution of exponentially decaying emission events along the line of sight. This is consistent with the idea that the solar atmosphere is heated everywhere by small energy deposition events.