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 2Y6 R. 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.