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Session 2 - Everything Else.
Display session, Friday, June 27
Ballroom C, Chair: Richard Canfield

[2.38] NOAA 7926: A Kinked, Submerging Ømega-loop ?

A. A. Pevtsov, R. C. Canfield (Montana State University)

Using vector magnetograms and X-ray images, we study the evolution of decaying active region NOAA AR 7926. This active region had bipolar structure with non-Hale polarity. Observations suggest that the following polarity of this active region was in fact the leading polarity of active region NOAA AR 7918 on the previous solar rotation. Analyzing the rotation rate of both active regions and the topology of their magnetic field, we conclude that they belong to a single magnetic system resembling a kinked Ømega loop. During the first rotation the upper part of the loop was exposed, forming the bipolar active region of normal (Hale) polarity. The rest of the Ømega loop had emerged on the time by the second rotation, giving the appearance of non-Hale polarity. The major soft X-ray coronal loops of NOAA AR 7926 closely relate to the weak magnetic field in the middle part of the region. In that area, the photospheric field stayed concave-down in the course of dissipation of the active region, and the coronal loops decreased their length. We also find that coronal loops decrease their height derived using E and W limb observations of the two active regions NOAA AR 7926 and NOAA AR 7918. Hence, we concluded that the magnetic field of the active region submerged under the photosphere.

Program listing for Friday