Journal
ASTRONOMY LETTERS-A JOURNAL OF ASTRONOMY AND SPACE ASTROPHYSICS
Volume 44, Issue 3, Pages 202-211Publisher
MAIK NAUKA/INTERPERIODICA/SPRINGER
DOI: 10.1134/S1063773718020056
Keywords
Sun; solar activity; sunspots; solar rotation
Categories
Funding
- Russian Foundation for Basic Research [16-02-00090]
- Program for Support of Leading Scientific Schools [NSh-7241.2016.2]
- Russian Academy of Sciences
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To investigate the differential rotation of sunspot groups using the Greenwich data, we propose an approach based on a statistical analysis of the histograms of particular longitudinal velocities in different latitude intervals. The general statistical velocity distributions for all such intervals are shown to be described by two rather than one normal distribution, so that two fundamental rotation modes exist simultaneously: fast and slow. The differentiality of rotation for the modes is the same: the coefficient at sin(2) in Faye's law is 2.87-2.88 deg/day, while the equatorial rotation rates differ significantly, 0.27 deg/day. On the other hand, an analysis of the longitudinal velocities for the previously revealed two differing populations of sunspot groups has shown that small short-lived groups (SSGs) are associated with the fast rotation mode, while large long-lived groups (LLGs) are associated with both fast and slow modes. The results obtained not only suggest a real physical difference between the two populations of sunspots but also give new empirical data for the development of a dynamo theory, in particular, for the theory of a spatially distributed dynamo.
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