Waiting time distribution of solar flares from a global perspective

TL;DR

This study analyzes the waiting time distribution of solar flares from a global perspective using data from Solar Orbiter and near-Earth spacecrafts, revealing complex statistical behaviors and the significance of long-range magnetic connections.

Contribution

It provides the first comprehensive global analysis of solar flare waiting times, incorporating far-side flares, and evaluates multiple statistical models to understand flare occurrence mechanisms.

Findings

WTD in the active region favors a log-normal distribution.

Global flare WTD cannot be fitted by standard distributions, showing a steep power-law tail.

Far-side flares influence the distribution, indicating long-range magnetic connections.

Abstract

The waiting time statistics of solar flares provides clues for the underlying physical mechanisms. However, flares occurring on the far-side have been missing in the statistics. In the 2024 May and June, the Solar Orbiter (SolO) spacecraft orbiting behind the Sun, together with near-Earth spacecrafts, provides a unique opportunity to study one of the most flare-productive active regions, NOAA \sar, over its lifetime, as well as the flare occurrence over the entire solar globe. Derived from time intervals between flare peak times, the waiting time distribution (WTD) is fitted by exponential, log-normal, power-law, and \levy functions with the maximum likelihood estimation method. The goodness of fit is evaluated by the Kolmogorov-Smirnov test, and the statistical models are discriminated by information criteria. The major statistical results are: the WTD of flares in the \sar leans towards the log-normal function, while that in the `normal' \rar towards the \levy function; the WTD of global flares defies the local Poisson hypothesis, and its overall profile cannot be reasonably fitted by any of the four candidate distributions, but its power-law tail $\Delta t^{-\alpha}$ is steeper ($\alpha>3$) than the theoretical expectations ($\alpha\le3$), due to the decreased number of long waiting times ($>10^4$ s) and the increased number of shorter waiting times when the far-side flares are taken into account. These results highlight the importance of studying the flare WTD from a global perspective, and suggest that the long-range magnetic connections in the corona may play a role in the flare occurrences.