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Session 8 - Corona III.
Oral session, Saturday, June 28
Ballroom A, Chair: Barry LaBonte
Polar plumes are magnetically open high density structures that are observed in the polar coronal holes. They arise from unipolar magnetic footpoints in between chromospheric network cells, and expand as they rise through the corona to altitudes of at least 15-20 solar radii. On timescales of hours, plumes are remarkably stable, quiescent structures; however, we find that plumes vary significantly in XUV intensity on time scales of a few minutes and length scales of about an arc minute, based on high cadence observations in the EIT 171A and 195A passbands. The observed variations propagate outward with speeds of about 300 km/sec. We demonstrate this effect in several plumes observed during different EIT high cadence pole observations; compare observed variations in the photospheric field, as measured simultaneously by MDI, to the intensity variations in the plumes; and suggest whether the outward motions represent physical structures or wave motion.
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