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Simulations of the sun's polar magnetic fields during sunspot cycle 21Regarding new bipolar magnetic regions as sources of flux, the evolution of the radial component of the solar photospheric magnetic field is simulated during 1976-1984, and the corresponding evolution of the line-of-sight polar fields as seen from earth is derived. The observed timing and strength of the polar-field reversal during cycle 21 can be accounted for by supergranular diffusion alone, for a diffusion coefficient of 800 sq km/sec. For an assumed 300 sq km/sec rate of diffusion, on the other hand, a poleward meridional flow with a moderately broad profile and a peak speed of 10 m/s reached at about 5 deg latitude is required to obtain agreement between the simulated and observed fields. Such a flow accelerates the transport of following-polarity flux to the polar caps, but also inhibits the diffusion of leading-polarity flux across the equator. For flows faster than about 10 m/s, the latter effect dominates, and the simulated polar fields reverse increasingly later and more weakly than the observed fields.
Document ID
19870056605
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Devore, C. Richard
(Naval Research Lab. Washington, DC, United States)
Sheeley, Neil R., Jr.
(U.S. Navy, Naval Research Laboratory, Washington DC, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Publication Information
Publication: Solar Physics
Volume: 108
Issue: 1 19
ISSN: 0038-0938
Subject Category
Solar Physics
Accession Number
87A43879
Funding Number(s)
CONTRACT_GRANT: DPR-W-14429
Distribution Limits
Public
Copyright
Other

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