Speaker
Description
First Name: Kostas
Last Name: Moraitis
Affiliation: University of Ioannina
All Authors: K. Moraitis, J.K. Thalmann
Abstract: This work examines the relative helicity and its current-carrying component contained in the area around the polarity inversion line (PIL) of the magnetic field, and also, their relation with solar eruptivity. For these, we study the evolution of the PIL helicities in a sample of 220 solar flares above the M1.0 clas, which were observed by HMI/SDO and originated from ~40 active regions. The computation of the PIL helicities is accomplished with the help of the respective relative field line helicities, the recently-developed proxies for the densities of the corresponding helicities, after first extrapolating for the 3D coronal magnetic field with a nonlinear force-free method. We find that, on average, for the stronger flares (above the M5.0 class) the PIL relative helicity experiences important decreases, >10%, during eruptive flares, while mixed changes are observed for confined flares. The strength of these changes agrees with that of the volume relative helicity. The PIL current-carrying helicity shows higher-magnitude decreases in both strong and weaker flares, reaching >20% average changes during the stronger eruptive flares. Moreover, the PIL current-carrying helicity’s flare-related variations exhibit the largest differences between eruptive and confined flares. We thus propose this PIL helicity as a reliable indicator of solar eruptivity.