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Solar Rotation over Solar Cycle 21

Published online by Cambridge University Press:  12 April 2016

Elisabeth Ribes ,
Istvan Vince ,
Pierre Mein  and
Eduardo Neto Ferreira
Elisabeth Ribes
Affiliation:
URA 326, Observatoire de Paris, 92195 Meudon, France
Istvan Vince
Affiliation:
Osservatorio Beograd, Beograd, Yugoslavia
Pierre Mein
Affiliation:
URA 326, Observatoire de Paris, 92195 Meudon, France
Eduardo Neto Ferreira
Affiliation:
URA 326, Observatoire de Paris, 92195 Meudon, France

Abstract

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Having measured the rotation rate of sunspots through solar cycle 21, from 1977 to 1983, we have found that the mean differential rotation averaged over this seven year record is similar to the grand average differential rotation determined by Howard et al. (1984) over the period 1921-1982. However, the rotation rate does change from year to year. These changes are evidenced by a steepening or a flattening of the mean differential rotation profile, as well as significant changes in the equatorial rate. The presence of a time-dependent pattern of azimuthal rolls inferred from the meridional circulation pattern of the sunspots offers a qualitative explanation of the observed rotation rates. The amplitude of the changes is almost one order of magnitude larger than that of the torsional oscillations found by Howard and LaBonte (1981).

Type
Part III Solar magnetism and large-scale flows
Information
International Astronomical Union Colloquium , Volume 130: The Sun and Cool Stars: activity, magnetism, dynamos , 1991 , pp. 241 - 245
Copyright
Copyright © Springer-Verlag 1991

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