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Area-Weighting of Sunspot Group Positions and Proper Motion Artifacts

Published online by Cambridge University Press:  12 April 2016

K. Petrovay
K. Petrovay*
Affiliation:
Eötvös University, Department of Astronomy, Budapest, Ludovika tér 2, H-1083Hungary

Abstract

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Two simple examples are presented to show that concepts about the physical nature of sunspot groups may significantly influence the statistical data analysis process. In particular, the second example shows that the well-known difference in the decay rates of preceding (p-) and following (f-) polarity parts of sunspot groups may lead to a fake proper motion effect when area-weighted group positions are used. This effect may be responsible for some recent contradictory findings concerning the motions of sunspot groups. It is therefore argued that while area-weighting is adequate when calculating the mean positions of p- and f-parts of a sunspot group separately, defining the position of the group as a whole by the unweighted average of the mean positions of the p- and f-parts is more satisfactory from the theoretical point of view (whenever it is possible to distinguish between spots of different polarities). Similarly, it is best not to “correct” sunspot proper motions for internal differential rotation within groups.

Type
Session 2. Theory of Active Region Structure
Information
International Astronomical Union Colloquium , Volume 141: The Magnetic and Velocity Fields of Solar Active Regions , 1993 , pp. 123 - 126
Copyright
Copyright © Astronomical Society of the Pacific 1993

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