Photospheric magnetic field variations accompanying the 2011 June 7   eruptive event
  From vector measurements of the photospheric magnetic field with the SDO/HMI instrument, we studied the field variations within the 2011 June 7 eruptive event related to the filament eruption (FE), flare, and coronal mass ejection (CME). We analyzed the variations in modulus (B), in radial (Br) and transversal (Bt) magnetic induction components, as well as in the field line inclination angle ({\alpha}) to the radial direction from the Sun center were. The conclusion is that the most probable cause for the FE onset being the trigger related to the flares and CME, as well as for Stage 1 of the filament dramatic acceleration, is {\guillemotleft}magnetic flux cancellation{\guillemotright} in several sites inside and around the filament channel. We assumed that the flare and the stage of the filament fastest acceleration are related to a spot emergence near the south-eastern filament footpoint, in which the field polarity and value satisfy a possibility of this field magnetic reconnection with the field surrounding the filament. We studied in detail the time variations in the field line inclination angles within different sites of the eruptive event. During the filament slow emergence, a decrease in the field line inclination angles was revealed to occur in its channel neighboring, whereas the field line inclination angles dramatically grew in the neutral line neighboring within the flare region after the flare onset. The flare ribbons at all the stages of their existence are shown to be located under the photosphere sites with the field modulus local maxima and with minima of the field line inclination angles. We show that, near the photospheric magnetic field polarity inversion line (PIL), the azimuth decreases after the flare onset, which means a decrease in the angle \b{eta} between PIL and the magnetic induction vector projection onto the sky plane. 
V.G. Fainshtein, Ya.I. Egorov, G.V. Rudenko
astro-ph.SR