On the origin of the eruptive events of February 2011: Magnetic field evolution and low corona structure

MANDRINI, C.H.; CRISTIANI, G.; CREMADES, H.; FRANCILE, C.; LÓPEZ, F.M.; GUTIÉRREZ-ESCATE, M.V.

Buenos Aires

Conferencia; Eleventh Latin American Conference on Space Geophysics; 2018

Asociación Latinoamericana de Geofísica Espacial

Active region (AR) NOAA 11158 produced several flares from 13 to 16 February 2011 accompanied by coronal mass ejections (CMEs) and subsequent EUV waves. AR 11158 was formed by two main bipoles that emerged almost simultaneously and a few minor ones, observed in vector magnetograms obtained with the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory.Flares and CMEs originated and evolved along different portions of the photospheric inversion line (PIL) following the displacement of the main bipoles, their sustained motion, and the built up of intense magnetic shear along the PILs where twisted flux ropes formed.  We model the coronal magnetic field of the AR along the three days and study its topology. We find the presence of a persistent magnetic null point, whose height and location changed as the photospheric field evolved. We propose that magentic reconnection occurring at the null neighborhood, forced by the photospheric motions, could decrease the magnetic tension above the flux ropes favouring  their repeated eruptions.