How do fast impulse CMEs related to powerful flares but unrelated to eruptive filaments appear and move?

Abstract

GOES-12/SXI and SDO/AIA data were used to examine the formation and initial stage of movement for several fast pulse ‘halo’-type coronal mass ejections (HCMEs) that were related to GOES M and X class flares but unrelated to solar filament eruptions. According to their formation, the HCMEs under study can be subdivided into three groups: (i) Most of the HCMEs studied resulted from broken equilibrium – presumably, due to an emerging new magnetic flux – of solitary wide loop-like emission structures identified with the future ejection observable in the 195Å channel a few hours before the mass ejection starts moving or before the relevant flare onset; (ii) a CME can form from several individual loop-like structures or, possibly, a loop arcade; (iii) for some HCMEs, their formation starts with a group of coronal loops moving upwards as first observed in the ‘hot’ 131Å channel. A few minutes later, loops start to move observable in images taken with the ‘colder’ 211Å channel, still later in the 193Å channel, and finally, in 171Å channel images. The moving loop-like structures affect the overlying coronal areas in such a way that a frontal HCME structure forms, its brightness increasing from the ‘hottest’ to the ‘coldest’ line. Moreover, loops are observed moving sunwards, towards the CME origin, resulting in an area of lower brightness forming behind the frontal structure. All the coronal mass ejections we studied started to move before the related solar flares appeared. The kinematics of the HCME’s under examination has been studied along, generally, curvilinear trajectories in the plane-of-sky. It has been concluded that two types of coronal mass ejections exist differing in their time speed profile determined by the area and magnetic configuration of the active area where the mass ejection originated. Homologous HCMEs – i.e. appearing in the same active area at different times – have the same speed profile.