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Coronal Mass Ejection: up close and personal


A coronal mass ejection (CME) blasted out from an active region that was just coming around the Sun's edge (May 9-10, 2011). Even in the close-up video of the CME observed by SDO in extreme ultraviolet light, the blast is not so apparent: it looks more like a flower opening its petals. However, the arcade of coiling magnetic field lines seen in profile are busily reconnecting after the blast (called post-flare loops) and put on a splendid show. The growing, expanding loop arcade with time is an illusion. This perceived expansion results from the magnetic reconnection process proceeding upward into the corona, forming new closed hot loops at successively higher levels in the 171 Angstrom channel. The lower loops, which get heated first, cool out of the 171 Angstrom channel sooner than the higher loops. These two effects produce an apparent rising loop system. That video clip shows about 20 hours of activity.

For a different view, SOHO's coronagraph, which blocks out the Sun (indicated by the white circle) to observe activity in the Sun's atmosphere, shows the event more clearly: the video clip shows a blossoming particle cloud as it roars away from the Sun and expands out into space over about a day. The cloud is moving at several millions of miles per hour.

Search Tag(s): 171, loops, active regions, eruption




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