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Global magnetic fields: variation of solar minima

Published online by Cambridge University Press:  05 July 2012

Andrey G. Tlatov  and
Vladimir N. Obridko
Andrey G. Tlatov
Affiliation:
Kislovodsk mountian astronomical station of the Pulkovo observatory, Gagarina str. 100, Kislovodsk, Russia email: [email protected]
Vladimir N. Obridko
Affiliation:
Pushkov Institute of Terrestrial Magnetism, Ionosphere & Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow RegionRussia, email: [email protected]
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Abstract

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The topology of the large-scale magnetic field of the Sun and its role in the development of magnetic activity were investigated using Hα charts of the Sun in the period 1887-2011. We have considered the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields. Such indices include: dipole-octopole index, area and average latitude of the field with dominant polarity in each hemisphere and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle.

The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the large-scale magnetic field has been slow and steadily changing during the past 130 years. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices, solar wind and Gleissberg cycle are discussed.

We also discuss the origin of the large-scale magnetic field. Perhaps the large-scale field leads to the generation of small-scale bipolar ephemeral regions, which in turn support the large-scale field. The existence of two dynamos: a dynamo of sunspots and a surface dynamo can explain phenomena such as long periods of sunspot minima, permanent dynamo in stars and the geomagnetic field.

Keywords

Solarlarge-scale magnetic fieldsolar activity
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S286: Comparative Magnetic Minima: Characterizing quiet times in the Sun and Stars , October 2011 , pp. 113 - 122
Copyright
Copyright © International Astronomical Union 2012

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