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Use of Yohkoh SXT in Measuring the Net Current and CME Productivity of Active RegionsIn our investigation of the correlation of global nonpotentiality of active regions to their CME productivity (Falconer, D.A. 2001, JGR, in press, and Falconer, Moore, & Gary, 2000, EOS 82, 20 S323), we use Yohkoh SXT images for two purposes. The first use is to help resolve the 180 degree ambiguity in the direction of the observed transverse magnetic field. Resolution of the 180 degree ambiguity is important, since the net current, one of our measures of global nonpotentiality, is derived from integrating the dot product of the transverse field around a contour (I(sub N)=(integral)BT(raised dot)dl). The ambiguity results from the observed transverse field being determined from the linear polarization, which gives the plane of the direction, but leaves a 180 degrees ambiguity. Automated methods to resolve the ambiguity ranging from the simple acute angle rule (Falconer, D.A. 2001) to the more sophisticated annealing method (Metcalf T.R. 1994). For many active regions, especially ones that are nearly potential these methods work well. But for very nonpotential active regions where the shear angle (the angle between the observed and potential transverse field) is near 90 degrees throughout large swaths along the main neutral line, both methods can resolve the ambiguity incorrectly for long segments of the neutral line. By determining from coronal images, such as those from Yohkoh/SXT, the sense of shear along the main neutral line in the active region, these cases can be identified and corrected by a modification of the acute angle rule described here. The second use of Yohkoh/SXT in this study is to check for the cusped coronal arcades of long-duration eruptive flares. This signature is an excellent proxy for CMEs, and was used by Canfield, Hudson, and McKenzie (1999 GRL V26, 6, 627-630). This work is funded by NSF through the Space Weather Program and by NASA through the Solar Physics Supporting Research and Technology Program.
Document ID
20020019963
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Falconer, D. A.
(Alabama Univ. Huntsville, AL United States)
Moore, R. L.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Gary, G. A.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Six, N. Frank
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Geophysics
Meeting Information
Meeting: Multi-wavelength Observations of Coronal Structures and Dynamics-Yohkoh 10th Anniversary
Location: Kona, HI
Country: United States
Start Date: January 21, 2002
End Date: January 24, 2002
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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