# Self-Organized Criticality in Solar and Stellar Flares: Are Extreme Events Scale-Free ?

## TL;DR

This study investigates whether extreme solar and stellar flares are fundamentally different from typical events, finding that most are scale-free and can be explained by a single physical mechanism, with only rare outliers suggesting different origins.

## Contribution

The paper provides evidence that extreme flares generally follow scale-free distributions, challenging the idea that the most extreme events are generated by different physical processes.

## Key findings

- Dragon-King outliers are rare in flare data.
- Flares follow power-law distributions with constrained slopes.
- Large datasets show deviations from ideal power laws.

## Abstract

We search for outliers in extreme events of statistical size distributions of astrophysical data sets, motivated by the {\sl Dragon-King hypothesis} of Sornette (2009), which suggests that the most extreme events in a statistical distribution may belong to a different population, and thus may be generated by a different phyiscal mechanism, in contrast to the strict power law behavior of {\sl self-organized criticality (SOC)} models. Identifying such disparate outliers is important for space weather predictions. Possible physical mechanisms to produce such outliers could be generated by sympathetic flaring. However, we find that Dragon-King events are not common in solar and stellar flares, identified in 4 out of 25 solar and stellar flare data sets only. Consequently, small, large, and extreme flares are essentially scale-free and can be modeled with a single physical mechanism. In very large data sets ($N \gapprox 10^4$) we find significant deviations from ideal power laws in almost all data sets. Neverthess, the fitted power law slopes constrain physcial scaling laws in terms of flare areas and volumes, which have the highest nonlinearity in their scaling laws.