A Streamer Ejection with Reconnection Close to the Sun

Abstract

We previously described coronal events that expand gradually outward over an interval of 1-2 days and then suddenly tear apart in the coronagraph's 2-6 R_solar field of view to form an outgoing flux rope and an inward system of collapsing loops. Now, we combine LASCO white-light images of the outer corona with spectrally resolved EIT images of the inner corona to describe a similar event for which the separation occurs closer to the Sun. The evolution of this 2006 July 1-2 event had four phases: (1) an expansion phase in which magnetic loops rise slowly upward and increase the amount of open flux in the adjacent polar coronal hole and in the low-latitude hole of opposite polarity; (2) a stretching phase in which the legs of the rising loops pinch together to form a current sheet; (3) a transition phase in which field line reconnection produces an outgoing flux rope and a hot cusp of new loops; and (4) an end phase in which the reconnected loops become visible at lower temperatures, and the outgoing flux rope plows through the slow material ahead of it to form a traveling bow wave. During this time, the photospheric field was relatively weak and unchanging, as if the eruption had a nonmagnetic origin. We suppose that coronal heating gradually overpowers magnetic tension and causes the streamer to separate into a system of collapsing loops and a flux rope that is carried outward in the solar wind.