MULTIFRACTAL SOLAR EUV INTENSITY FLUCTUATIONS AND THEIR IMPLICATIONS FOR CORONAL HEATING MODELS

• Published in: The Astrophysical journal 2016-11, Vol.831 (2), p.186
• Main Authors: Cadavid, A. C., Rivera, Y. J., Lawrence, J. K., Christian, D. J., Jennings, P. J., Rappazzo, A. F.
• Format: Article
• Language: English
• Subjects: Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Atmospheric models; Computational fluid dynamics; COMPUTERIZED SIMULATION; Constraint modelling; Coronal heating; Coronal loops; Correlation; CORRELATIONS; DEFEROXAMINE; DISTRIBUTION FUNCTIONS; EMISSION; Emission analysis; Emissions; EXTREME ULTRAVIOLET RADIATION; FLUCTUATIONS; Fluid flow; Heating; MAGNETOHYDRODYNAMICS; Noise; Ohmic dissipation; PROBABILITY; Probability distribution; Probability distribution functions; Radiance; SCALING; SIGNAL-TO-NOISE RATIO; Solar activity; SOLAR CORONA; Solar EUV; Solar observatories; SOLAR RADIATION; SPACE; SUN; Sun: corona; Sun: transition region; Time series; Variation
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/0004-637X/831/2/186

ABSTRACT We investigate the scaling properties of the long-range temporal evolution and intermittency of Atmospheric Imaging Assembly/Solar Dynamics Observatory intensity observations in four solar environments: an active region core, a weak emission region, and two core loops. We use two approaches: the probability distribution function (PDF) of time series increments and multifractal detrended fluctuation analysis (MF-DFA). Noise taints the results, so we focus on the 171 Å waveband, which has the highest signal-to-noise ratio. The lags between pairs of wavebands distinguish between coronal versus transition region (TR) emission. In all physical regions studied, scaling in the range of 15-45 minutes is multifractal, and the time series are anti-persistent on average. The degree of anti-correlation in the TR time series is greater than that for coronal emission. The multifractality stems from long-term correlations in the data rather than the wide distribution of intensities. Observations in the 335 Å waveband can be described in terms of a multifractal with added noise. The multiscaling of the extreme-ultraviolet data agrees qualitatively with the radiance from a phenomenological model of impulsive bursts plus noise, and also from ohmic dissipation in a reduced magnetohydrodynamic model for coronal loop heating. The parameter space must be further explored to seek quantitative agreement. Thus, the observational "signatures" obtained by the combined tests of the PDF of increments and the MF-DFA offer strong constraints that can systematically discriminate among models for coronal heating.