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Changes in measured vector magnetic fields when transformed into heliographic coordinatesThe changes that occur in measured magnetic fields when they are transformed into a heliographic coordinate system are investigated. To carry out this investigation, measurements of the vector magnetic field of an active region that was observed at 1/3 the solar radius from disk center are taken, and the observed field is transformed into heliographic coordinates. Differences in the calculated potential field that occur when the heliographic normal component of the field is used as the boundary condition rather than the observed line-of-sight component are also examined. The results of this analysis show: (1) that the observed fields of sunspots more closely resemble the generally accepted picture of the distribution of umbral fields if they are displayed in heliographic coordinates; (2) that the differences in the potential calculations are less than 200 G in field strength and 20 deg in field azimuth outside sunspots; and (3) that differences in the two potential calculations in the sunspot areas are no more than 400 G in field strength but range from 60 to 80 deg in field azimuth in localized umbral areas.
Document ID
19870053116
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hagyard, M. J.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Publication Information
Publication: Solar Physics
Volume: 107
Issue: 2, 19
ISSN: 0038-0938
Subject Category
Solar Physics
Accession Number
87A40390
Distribution Limits
Public
Copyright
Other

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