Dynamic Precursors of Flares in Active Region NOAA 10486

TL;DR

This study uses four methods to identify precursors of solar flares in active region NOAA 10486, revealing specific signatures that indicate imminent flare activity through magnetic and morphological indicators.

Contribution

The paper introduces and applies four novel and existing methods to detect flare precursors, combining magnetic field analysis and flare activity tracking in a comprehensive approach.

Findings

WGM indicates magnetic non-potentiality increases before flares.

S(lf) reflects overall active region morphology changes prior to flares.

Temporal patterns of small x-ray flares serve as precursors.

Abstract

Four different methods are applied here to study the precursors of flare activity in the Active Region NOAA 10486. Two approaches track the temporal behaviour of suitably chosen features (one, the weighted horizontal gradient WGM, is generalised form the horizontal gradient of the magnetic field, GM; another is the sum of the horizontal gradient of the magnetic field, GS, for all sunspot pairs). WGM is a photospheric indicator that is a proxy measure of magnetic non-potentiality of a specific area of the active region, i.e. it captures the temporal variation of the weighted horizontal gradient of magnetic flux summed up for the region where opposite magnetic polarities are highly mixed. The third one, referred to as the separateness parameter, S(lf), considers the overall morphology. Further, GS and S(lf) are photospheric newly defined quick-look indicators of the polarity mix of the entire active region. The fourth method is tracking the temporal variation of small x-ray flares, their times of succession and their energies observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager instrument. All approaches yield specific pre-cursory signatures for the imminence of flares.