Regularities in the growth of background magnetic fields |
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| Authors: | O A Andryeyeva Ya I Zyelyk N N Stepanian Yu T Tsap |
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| Institution: | 1.Crimean Astrophysical Observatory,Crimea,Ukraine;2.Space Research Institute,National Academy of Sciences of Ukraine and National Space Agency of Ukraine,Kiev,Ukraine |
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| Abstract: | The cyclicity in the latitudinal distribution of the growth and decay rates of the total magnetic fluxes for weak magnetic
fields is investigated. The synoptic maps of the line-of-sight solar magnetic field strength obtained at the Kitt Peak Observatory
(USA) from January 1, 1977, to September 30, 2003, are used as the observational material. The latitudinal distributions of
the growth rates of total magnetic fluxes with various strengths constructed from them and their evolution during three solar
cycles have been compared with the analogous distribution of the total powers of rotation with various periods as well as
the relative sunspot numbers and areas. The results obtained allow a unified picture of the development of solar cycles for
weak and strong magnetic fields to be formulated. A new cycle begins with the growth of weak magnetic fields with a strength
of 0–200 G at latitudes 20°–25° in both hemispheres. This occurs one year before the activity minimum determined from sunspots.
Two years later, the growth rate of the total magnetic flux, which begins to propagate equatorward and poleward, reaches a
maximum. This process coincides with the onset of the growth of strong sunspot magnetic fields at the corresponding latitudes
and the formation of zones with a stable rotation. Subsequently, a fall-off in growth rate and then a flux decay for weak
magnetic fields correspond to the growth of the sunspot areas. In light of the dynamo theory, the results obtained suggest
that strong and weak magnetic fields are generated near the bottom of the convection zone, while the observed differences
in their behavior are determined by the interaction of emerging magnetic flux tubes of various strengths with turbulent plasma
motions inside the Sun. |
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