The Universality of Power Law Slopes in the Solar Photosphere and Transition Region Observed with HMI and IRIS

TL;DR

This study demonstrates the universal power law slopes in the size distributions of various solar phenomena across the photosphere and transition region, using magnetogram data from HMI and IRIS, confirming SOC theory predictions.

Contribution

It provides empirical evidence for the universality of SOC-inferred flux size distributions in the solar atmosphere, validated across different datasets and physical processes.

Findings

High correlation (CCC=0.90) between IRIS and HMI data.

Datasets with balanced magnetic flux match SOC-predicted slope a_F=1.80.

Results align with previous studies indicating a_F≈1.85.

Abstract

We compare the size distributions of self-organized criticality (SOC) systems in the solar photosphere and the transition region, using magnetogram data from Helioseismic and Magnetic Imager (HMI) and Interface Region Imaging Spectrograph (IRIS)} 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 a_F=1.80 (for mean fluxes F), 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.~(2009), a_F=1.85 +/- 0.14.