On the non-Kolmogorov nature of flare-productive solar active regions

TL;DR

This study analyzes the magnetic power spectral properties of solar active regions, revealing that flare-productive regions have higher and more stable magnetic power indices, which can improve flare prediction models.

Contribution

It demonstrates the significance of the magnetic power index and its temporal stability in distinguishing flare-productive regions, advancing space weather forecasting methods.

Findings

Flare-productive regions have higher magnetic power indices (>2)

Flare-quiet regions show high temporal variance in the index

Stable high indices over days correlate with flare productivity

Abstract

A magnetic power spectral analysis is performed on 53 solar active regions, observed from August 2011 to July 2012. Magnetic field data obtained from the Helioseismic and Magnetic Imager, inverted as Active Region Patches, are used to study the evolution of the magnetic power index as each region rotates across the solar disk. Active regions are classified based on the number, and sizes, of solar flares they produce, in order to study the relationship between flare productivity and the magnetic power index. The choice of window size and inertial range plays a key role in determining the correct magnetic power index. The overall distribution of magnetic power indices has a range of $1.0-2.5$. Flare-quiet regions peak at a value of 1.6, however flare-productive regions peak at a value of 2.2. Overall, the histogram of the distribution of power indices of flare-productive active regions is well separated from flare-quiet active regions. Only 12\% of flare-quiet regions exhibit an index greater than 2, whereas 90\% of flare-productive regions exhibit an index greater than 2. Flare-quiet regions exhibit a high temporal variance (i.e, the index fluctuates between high and low values), whereas flare-productive regions maintain an index greater than 2 for several days. This shows the importance of including the temporal evolution of active regions in flare prediction studies, and highlights the potential of a 2-3 day prediction window for space weather applications.