Comparison of the Scaling Properties of EUV Intensity Fluctuations in Coronal Hole and Quiet-Sun Regions

• Published in: The Astrophysical journal Vol. 886; no. 2; pp. 143 - 154
• Main Authors: Cadavid, Ana Cristina, Miralles, Mari Paz, Romich, Kristine
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.12.2019; IOP Publishing
• Subjects: Astrophysics; Atmospheric models; Coronal holes; Fluctuations; Magnetic fields; Polarity; Quiet solar corona; Quiet sun; Scaling; Solar activity; Solar coronal holes; Solar coronal loops; Solar extreme ultraviolet emission; Solar magnetic fields; Solar observatories; Sun
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab4d4e

Using detrended fluctuation analysis and rescaled range analysis, we investigate the scaling properties of extreme ultraviolet (EUV) intensity fluctuations of low-latitude coronal holes (CHs) and neighboring quiet-Sun (QS) regions in signals obtained with the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly instrument. Contemporaneous line-of-sight SDO/Helioseismic and Magnetic Imager magnetic fields provide a context for the physical environment. We find that the intensity fluctuations in the time series of EUV images present at each spatial point a scaling symmetry over the range ∼20 minute to ∼1 hr. Thus we are able to calculate a generalized Hurst exponent and produce image maps, not of physical quantities like intensity or temperature, but of a single dynamical parameter that sums up the statistical nature of the intensity fluctuations at each pixel. In QS regions and in CHs with magnetic bipoles, the scaling exponent (1.0 < ≤ 1.5) corresponds to anticorrelated turbulent-like processes. In CHs, and in QS regions primarily associated with (open) magnetic field of dominant polarity, the generalized exponent (0.5 < < 1) corresponds to positively correlated (persistent) processes. We identify a tendency for ∼ 1 near CH boundaries and in other regions in which open and closed magnetic fields are in proximity. This is a signature of an underlying 1/f type process that is characteristic for self-organized criticality and shot-noise models.