Properties of Flare-Imminent versus Flare-Quiet Active Regions from the Chromosphere through the Corona II: NonParametric Discriminant Analysis Results from the NWRA Classification Infrastructure (NCI)

TL;DR

This study uses nonparametric discriminant analysis on multi-wavelength solar data to identify parameters that distinguish active regions likely to produce imminent flares, achieving high classification skill.

Contribution

It introduces a comprehensive set of image-based parameters and demonstrates their effectiveness in flare prediction using nonparametric discriminant analysis.

Findings

Higher-order moments of running difference images indicate flare-imminent regions show small-scale brightening.

Coronal emission parameters, especially from the 94AA filter, are strong flare predictors.

Classification scores suggest reliable differentiation between flare-producing and quiet regions.

Abstract

A large sample of active-region-targeted time-series images from the Solar Dynamics Observatory / Atmospheric Imaging Assembly, the AIA Active Region Patch database ("AARPs", Paper I: Dissauer et al 2022) is used to investigate whether parameters describing the coronal, transition region, and chromospheric emission can differentiate a region that will imminently produce a solar flare from one that will not. Parametrizations based on moment analysis of direct and running-difference images provide for physically-interpretable results from nonparametric discriminant analysis. Across four event definitions including both 24hr and 6hr validity periods, 160 image-based parameters capture the general state of the atmosphere, rapid brightness changes, and longer-term intensity evolution. We find top Brier Skill Scores in the 0.07--0.33 range, True Skill Statistics in the 0.68--0.82 range (both depending on event definition), and Receiver Operating Characteristic Skill Scores above 0.8. Total emission can perform notably as can steeply increasing or decreasing brightness, although mean brightness measures do not, demonstrating the well-known active-region-size/flare-productivity relation. Once a region is flare productive, the active-region coronal plasma appears to stay hot. The 94AA filter data provides the most parameters with discriminating power, with indications that it benefits from sampling multiple physical regimes. In particular, classification success using higher-order moments of running difference images indicate a propensity for flare-imminent regions to display short-lived small-scale brightening events. Parameters describing the evolution of the corona can provide flare-imminent indicators, but at no preference over "static" parameters. Finally, all parameters and NPDA-derived probabilities are available to the community for additional research.