4 years ago

A Global Survey of EUV Corona Power Spectra.

Karl Battams, Robert S. Weigel, Brendan M. Gallagher

We present results of a global survey of single-pixel intensity power spectra from a 12-hour time period on June 26, 2013 in a 1600x1600 pixel region from five channels of the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument. We extract single-pixel time series from a derotated image sequence, fit models to the power spectra of these time series, and study the spatial dependence of the model parameters. Two power spectra models are considered: (1) a 3-parameter power-law + tail model and (2) a power-law + tail model + 3-parameter localized Gaussian, which models a periodicity. In general, spectra are well-described by at least one of these two models for all pixel locations, with an average data/model correlation of 0.93 and a standard deviation of 0.1. The spatial distribution of best-fit parameter values for the models are shown to provide new and unique insights into turbulent, quiescent and periodic features in the EUV solar corona and upper photosphere. Findings include: individual model parameters correspond clearly and directly to visible solar features; detection of numerous quasi-periodic 3- and 5-minute oscillations; observational identification of concentrated magnetic flux as regions of largest power-law indices (n); identification of unique spectral features of coronal holes and filaments; identification of sporadic and pervasive 5-minute oscillations throughout the corona; detection of the known global ~4.0-minute chromospheric oscillation; "Coronal Bullseyes" appearing as radially decaying periodicities over sunspots and sporadic foot-point regions; and "Penumbral Periodic Voids" appearing as broad rings around sunspots in 1600 and 1700 {\AA} in which spectra contain no statistically significant periodic component.

Publisher URL: http://arxiv.org/abs/1707.02448

DOI: arXiv:1707.02448v2

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