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The hemispheric asymmetry of solar activity during the last century and the solar dynamo

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Title The hemispheric asymmetry of solar activity during the last century and the solar dynamo
 
Creator GOEL, A
CHOUDHURI, AR
 
Subject deep meridional flow
flux-transport dynamo
polar faculae
stochastic fluctuations
maunder minimum
magnetic-field
model
cycle
circulation
regions
sun: activity
sun: magnetic fields
sunspots
 
Description We believe the Babcock-Leighton process of poloidal field generation to be the main source of irregularity in the solar cycle. The random nature of this process may make the poloidal field in one hemisphere stronger than that in the other hemisphere at the end of a cycle. We expect this to induce an asymmetry in the next sunspot cycle. We look for evidence of this in the observational data and then model it theoretically with our dynamo code. Since actual polar field measurements exist only from the 1970s, we use the polar faculae number data recorded by Sheeley (1991, 2008) as a proxy of the polar field and estimate the hemispheric asymmetry of the polar field in different solar minima during the major part of the twentieth century. This asymmetry is found to have a reasonable correlation with the asymmetry of the next cycle. We then run our dynamo code by feeding information about this asymmetry at the successive minima and compare the results with observational data. We find that the theoretically computed asymmetries of different cycles compare favorably with the observational data, with the correlation coefficient being 0.73. Due to the coupling between the two hemispheres, any hemispheric asymmetry tends to get attenuated with time. The hemispheric asymmetry of a cycle either from observational data or from theoretical calculations statistically tends to be less than the asymmetry in the polar field (as inferred from the faculae data) in the preceding minimum. This reduction factor turns out to be 0.43 and 0.51 respectively in observational data and theoretical simulations.
 
Publisher SCIENCE PRESS
 
Date 2011-08-29T02:46:11Z
2011-12-26T12:58:21Z
2011-12-27T05:48:04Z
2011-08-29T02:46:11Z
2011-12-26T12:58:21Z
2011-12-27T05:48:04Z
2009
 
Type Article
 
Identifier RESEARCH IN ASTRONOMY AND ASTROPHYSICS, 9(1), 115-126
1674-4527
http://dspace.library.iitb.ac.in/xmlui/handle/10054/11928
http://hdl.handle.net/10054/11928
 
Language en