Astronomy and Astrophysics – Astronomy
Scientific paper
May 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...180.5102w&link_type=abstract
American Astronomical Society, 180th AAS Meeting, #51.02; Bulletin of the American Astronomical Society, Vol. 24, p.813
Astronomy and Astrophysics
Astronomy
Scientific paper
The San Fernando Observatory Video Spectra-Spectroheliograph (VS(2) HG) produces simultaneous spectra-spectroheliograms in two orthogonal polarizations; during four successive scans, all four Stokes vectors are recorded over a spectral region approximately 1.5 Angstroms wide, with pixels of 8 m Angstroms in the spectral direction and 0.46 seconds of arc in the spatial direction. Since each individual scan produces a continuum, line core, and Doppler map, these are both simultaneous and co-spatial, essentially by definition. The continuum images from each scan are used to align the separate scans of Stokes Q, U, and V. From these aligned scans, maps of the vector magnetic field are produced. A brief description of the VS(2) HG can be found in Lawrence, Chapman, and Walton (1991), Ap. J. 375, 771; a detailed description of the data processing procedure is in preparation. We observed active region NOAA 6659 using the VS(2) HG on 7 June and 10 through 15 June 1991, a period from two days before to six days after its central meridian passage. The Doppler maps from the 7th and the 10th show a blueshifted area just to the west of the northernmost sunspot of the group. This area was especially prominent on the 10th, and was co-spatial with the west ribbon as seen in Hα of an M3.2 flare which occurred at 1654 UT. (This region produced a very large flare (X12.0) at 11 June 0229 UT, but as of this writing, we don't have the precise location of this flare.) The vector maps show a strong tangential component of the magnetic field in this area. The direction of the tangential field changes rapidly across the area of the blueshift. The later observations (12 and 13 June) show what, given the disk position, appears to be an area of downflow in the same area: i.e., a redshift on the disk center side and a blueshift on the limbward side. We will show and discuss further the maps at the meeting. This research has been partially supported by NASA grant NAGW-2453 and NSF grant ATM-9115111.
Chapman Gary A.
David R. S.
Walton Stephen R.
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