AUTHOR=Aschwanden Markus J. , Nhalil Nived Vilangot 

TITLE=The universality of power law slopes in the solar photosphere and transition region observed with HMI and IRIS

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2023.1099346

DOI=10.3389/fspas.2023.1099346

ISSN=2296-987X

ABSTRACT=<p>We compare the size distributions of <italic>self-organized criticality (SOC)</italic> systems in the solar photosphere and the transition region, using magnetogram data from <italic>Helioseismic and Magnetic Imager (HMI)</italic> and <italic>Interface Region Imaging Spectrograph (IRIS)</italic> data. For each dataset we fit a combination of a Gaussian and a power law size distribution function, which yields information on four different physical processes: (i) Gaussian random noise in IRIS data; (ii) spicular events in the plages of the transition region (described by power law size distribution in IRIS data); (iii) salt-and-pepper small-scale magnetic structures (described by the random noise in HMI magnetograms); and (iv) magnetic reconnection processes in flares and nanoflares (described by power law size distributions in HMI data). We find a high correlation (CCC = 0.90) between IRIS and HMI data. Datasets with magnetic flux balance are generally found to match the SOC-predicted power law slope <italic>α</italic><sub><italic>F</italic></sub> = 1.80 (for mean fluxes <italic>F</italic>), but exceptions occur due to arbitrary choices of the HMI field-of-view. The matching cases confirm the universality of SOC-inferred flux size distributions, and agree with the results of Parnell et al. (ApJ, 2009, 698, 75–82), <italic>α</italic><sub><italic>F</italic></sub> = 1.85 ± 0.14.</p>