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Yohkoh SXT Full-Resolution Observations of Sigmoids: Structure, Formation, and Eruption View all abstracts by submitter

Richard Canfield   Submitted: 2007-08-01 09:23

We study the structure of 107 bright sigmoids using full-resolution (2 farcs 5 pixels) images from the Yohkoh Soft X-Ray Telescope obtained between December 1991 and December 2001. We find that none of these sigmoids are made of single loops of S or inverse-S shape - all comprise a pattern of multiple loops. We also find that all S-shaped sigmoids are made of right-bearing loops, and all S-1-shaped sigmoids, left-bearing loops, without exception. We co-align the SXT images with Kitt Peak magnetograms to determine the magnetic field directions in each sigmoid. We use a potential-field source surface model to determine the direction of the overlying magnetic field. We find that sigmoids for which the relative orientation of these two fields has a parallel component outnumber anti-parallel ones by more than an order of magnitude. We find that the number of sigmoids per AR region varies with the solar cycle in a manner that is consistent with this finding. Finally, those few sigmoids that are anti-parallel erupt roughly twice as often as those that are parallel. We briefly discuss the implications of these results in terms of formation and eruption mechanisms of flux tubes and sigmoids.

Authors: Richard C. Canfield, Maria D. Kazachenko, Loren W. Acton, D. H. Mackay, Ji Son, Tanya L. Freeman
Projects: None

Publication Status: ApJ Letters, submitted
Last Modified: 2007-08-01 09:24
Go to main E-Print page  Helioseismic Holography of Simulated Solar Convection and
Prospects for the Detection of Small-Scale Subsurface Flows  Segmentation of loops from coronal EUV images  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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