OBSERVING FLUX ROPE FORMATION DURING THE IMPULSIVE PHASE OF A SOLAR ERUPTION

Abstract

Magnetic flux rope is believed to be an important structural component of\ncoronal mass ejections (CMEs). While there exist much observational evidence of\nthe flux rope after the eruption, e.g., as seen in remote-sensing coronagraph\nimages or in-situ solar wind data, the direct observation of flux ropes during\nCME impulsive phase has been rare. In this Letter, we present an unambiguous\nobservation of a flux rope still in the formation phase in the low corona. The\nCME of interest occurred above the east limb on 2010 November 03 with\nfootpoints partially blocked. The flux rope was seen as a bright blob of hot\nplasma in AIA 131 \\AA\\ passband (peak temperature ~11 MK) rising from the core\nof the source active region, rapidly moving outward and stretching upward the\nsurrounding background magnetic field. The stretched magnetic field seemed to\ncurve-in behind the core, similar to the classical magnetic reconnection\nscenario in eruptive flares. On the other hand, the flux rope appeared as a\ndark cavity in AIA 211 \\AA\\ passpand (2.0 MK) and 171 \\AA\\ passband (0.6 MK);\nin these relatively cool temperature bands, a bright rim clearly enclosed the\ndark cavity. The bright rim likely represents the pile-up of the surrounding\ncoronal plasma compressed by the expanding flux rope. The composite structure\nseen in AIA multiple temperature bands is very similar to that in the\ncorresponding coronagraph images, which consists of a bright leading edge and a\ndark cavity, commonly believed to be a flux rope.\n