The origin of a series of EUV confined eruptions

M. L. LUONI; M. LÓPEZ FUENTES; P. DÉMOULIN; C. H. MANDRINI; G. CRISTIANI; M. POISSON

Viena

Congreso; International Astronomical Union General Assembly 2018; 2018

International Astronomical Union

We analyze a series of EUV confined eruptions that occurred in active region (AR) NOAA 11476. All the events were associated to M-class flares. We use observations in multiple wavelengths (EUV, X-rays,Halpha, and magnetograms) from instruments in space and on the ground. From this set of events, we discuss in particular the one on 09 May 2012. The magnetic configuration showed the presence of two rotating bipoles within the following polarity of the AR. This evolution was present along some tens of hours before the studied event and continued even later. During this period the magnetic flux of both bipoles was continuously decreasing. A minifilament with a length of ~ 30 arcsec lay along the photospheric inversion line of the largest bipole. The minifilament was observed to erupt at ~ 12:23 UT accompanied by an M4.7 flare having its GOES peak at ~ 12:32 UT. Consequently, dense material, as well as twist, was injected along closed loops in the form of a very broad ejection whose morphology resembles that of typical Halpha surges. We conclude that, as in other examples explaining jets, standard or blow out, the flare and eruption can be explained as due to two reconnection processes, one occurring below the erupting minifilament and another one between the minifilament itself and overlying magnetic loops; this second process brings the minifilament plasma and that of the loops where it is embedded within reconnected closed loops. Analyzing the magnetic topology using a force-free model of the coronal field, we identify the location of quasi-separatix layers (QSLs), where reconnection is prone to occur, and present a detailed interpretation of the chromospheric and coronal eruption observations. In particular, this event, contrary to what has been proposed in several models explaining surges and/or jets, is not originated by magnetic flux emergence but by magnetic flux cancellation accompanied by the rotation of the bipoles. In fact, the conjunction of these two processes, seems to be at the origin of a series of homologous events that occurred in AR 11476 from 08 to 10 May 2012.