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Open magnetic fields in active regionsSoft X-ray images and magnetograms of several active regions and coronal holes are examined which support the interpretation that some of the dark X-ray gaps seen between interconnecting loops and inner cores of active regions are foot points of open field lines inside the active regions. Characteristics of the investigated dark gaps are summarized. All the active regions with dark X-ray gaps at the proper place and with the correct polarity predicted by global potential extrapolation of photospheric magnetic fields are shown to be old active regions, indicating that field opening is accomplished only in a late phase of active-region development. It is noted that some of the observed dark gaps probably have nothing in common with open fields, but are either due to the decreased temperature in low-lying portions of interconnecting loops or are the roots of higher and less dense or cooler loops.
Document ID
19780039116
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Svestka, Z.
(American Science and Engineering, Inc. Cambridge, MA, United States)
Solodyna, C. V.
(American Science and Engineering, Inc. Cambridge, Mass., United States)
Howard, R.
(Hale Observatories Pasadena, Calif., United States)
Levine, R. H.
(Harvard College Observatory and Smithsonian Astrophysical Observatory, Center for Astrophysics, Cambridge Mass., United States)
Date Acquired
August 9, 2013
Publication Date
December 1, 1977
Publication Information
Publication: Solar Physics
Volume: 55
Subject Category
Solar Physics
Accession Number
78A23025
Funding Number(s)
CONTRACT_GRANT: NGR-09-140-015
CONTRACT_GRANT: NAS5-3949
CONTRACT_GRANT: NAS8-27758
Distribution Limits
Public
Copyright
Other

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