Coronal Fourier power spectra: implications for coronal heating and coronal seismology
Monday, 15 December 2014
The dynamics of regions of the solar corona are investigated using AIA 171 and 193 Angstrom data. It is shown that the mean Fourier power spectra of emission from active region cores, above sunspots, in loop footpoints and in the quiet Sun, follow an approximate power-law behaviour. We show that power-law power-spectra can be formed by summing a distribution of exponentially decaying emission events along the line of sight, consistent with the idea that the corona is heated everywhere by small energy deposition events. We also examine changes in Fourier power spectrum as a function of coronal loop height to look for evidence of a preferred location to coronal heating. The observed power-law power spectra also have implications for coronal seismology, as all existing observational studies do not take into account the power-law power spectrum of the coronal emission and its attendant statistical properties. We show that random fluctuations in the emission can be mis-identified as oscillatory signal, and give suggestions on how to detect oscillatory motions above a background power-law power spectrum.