Cycle dependence of the longitudinal-latitudinal sunspot motion correlations

Heliophysical Observatory of the Hungarian Academy of Sciences 4010 Debrecen PO Box 30, Hungary e-mail: murakozyj@puma.unideb.hu; ludmany@tigris.unideb.hu

Received: 9 August 2007
Accepted: 10 April 2008

Abstract

Aims. It is well known that the azimuthal and meridional shifts of sunspots are correlated and that the correlation exhibits a latitudinal distribution, which is expected due to the Coriolis effect. We study the temporal behaviour of this latitudinal distribution.

Methods. We analyze the daily positions of sunspot groups, provided by the Debrecen Photoheliographic Data and the Greenwich Photoheliographic Results and correlation values, which were mapped in  latitudinal bins. The latitudinal distributions were examined for each year.

Results. We derive a sunspot-motion correlation that exhibits a Coriolis-type latitudinal distribution on long timescales, which are typical for the yearly distributions; at cycle maximum, however, unexpected distortions can occur.

Conclusions. The causes of the weakening of the Coriolis-pattern remain unclear. Possible relations of the phenomenon to the Gnevyshev-gap, the polarity reversal of the main magnetic field, and some mid-period fluctuations are discussed.