Abstract Details

Name: Prabir Mitra
Affiliation: Udaipur Solar Observatory, Physical Research Laboratory
Conference ID: ASI2021_519
Title : On the Cause of Extremely Repetitive and Energetic Flare Productivity of Solar Active Region NOAA 12673
Authors and Co-Authors : Prabir K. Mitra (Udaipur Solar Observatory, Physical Research Laboratory), Bhuwan Joshi (Udaipur Solar Observatory, Physical Research Laboratory)
Abstract Type :
Abstract Category : Sun and the Solar System
Abstract : It is well accepted that solar transient phenomena e.g., flares, prominence eruptions, solar jets etc., are powered by catastrophic release of magnetic free energy. Therefore, a quantitative analysis of magnetic characteristics of the solar active regions (ARs) is extremely important to explore the physics of solar eruptions and their short term predictions. A few statistical surveys carried out so far, have elucidated that activities produced in ARs, in view of their frequency of occurrence and corresponding energetics, significantly depend on strength, configuration and topology of magnetic fields. In this work, we look into the detailed evolution of the exceptionally flare productive active region NOAA 12673, in order to understand the factors responsible for its extremely active nature. Notably, this active region appeared during solar minimum phase and produced 4 X-class and 27 M-class flares including the largest flare of the solar cycle 24, within a period of seven days. Our analysis revealed that this active region appeared as a simple α-type active region but quickly became complex and eventually evolved into the most complex δ-type active region. Further, its overall activity can be characterized by few distinct periods which were temporarily well separated. The analysis of Non-linear Force Free Field extrapolation complemented by computation of quasi-separatrix layers and twist numbers, suggest development and subsequent decay of complex coronal configuration including null points and separators in different locations within the active region volume and a number of highly twisted flux ropes to be responsible for its periodic activity. Additionally, we calculate the evolution of current and magnetic free energy stored in the active region which provides important insights in flare productivity of active regions in general.