Testing Self-Organized Criticality Across the Main Sequence using Stellar Flares from TESS

TL;DR

This study analyzes TESS data to test if stellar flares across the main sequence follow self-organized criticality, revealing a universal flare distribution that suggests stars maintain a critical magnetic state.

Contribution

It provides the first large-scale comparison of stellar flare distributions across spectral types, supporting the idea of a universal critical state in stellar coronae.

Findings

All main sequence stars show flare distributions similar to the Sun.

Flare frequency distributions are independent of stellar mass or age.

Stars may universally maintain a critical magnetic state.

Abstract

Self-organized criticality describes a class of dynamical systems that maintain themselves in an attractor state with no intrinsic length or time scale. Fundamentally, this theoretical construct requires a mechanism for instability that may trigger additional instabilities locally via dissipative processes. This concept has been invoked to explain nonlinear dynamical phenomena such as featureless energy spectra that have been observed empirically for earthquakes, avalanches, and solar flares. If this interpretation proves correct, it implies that the solar coronal magnetic field maintains itself in a critical state via a delicate balance between the dynamo-driven injection of magnetic energy and the release of that energy via flaring events. All-sky high-cadence surveys like the Transiting Exoplanet Survey Satellite (TESS) provide the necessary data to compare the energy distribution of flaring events in stars of different spectral types to that observed in the Sun. We identified $\sim 10^6$ flaring events on $\sim 10^5$ stars observed by TESS at 2-minute cadence. By fitting the flare frequency distribution for different mass bins, we find that all main sequence stars exhibit distributions of flaring events similar to that observed in the Sun, independent of their mass or age. This may suggest that stars universally maintain a critical state in their coronal topologies via magnetic reconnection events. If this interpretation proves correct, we may be able to infer properties of magnetic fields, interior structure, and dynamo mechanisms for stars that are otherwise unresolved point sources.