Dynamic Precursors of Flares in Active Region NOAA 10486

摘要

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 hori- zontal gradient W G (M) , is the generalized form of the horizontal gradient of the magnetic field, G (M) ; the other is the sum of the horizontal gradient of the magnetic field, G (S) , for all sunspot pairs). W G (M) 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 (l-f) , considers the overall morphology. Further, G (S) and S (l-f) 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.