A study of the north-south asymmetry of sunspot area during solar cycle 23

Partha Chowdhury1* and B. N. Dwivedi2
1Department of Physics, University of Calcutta, Kolkata, 700009, India
2Department of Applied Physics, Banaras Hindu University, Varanasi 221005, India

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Solar activity indices vary over the Sun’s disk, and various activity parameters are not considered to be symmetric between the northern and southern hemispheres of the Sun. The north-south asymmetries of different solar indices provide an important clue to understanding solar dynamo action, especially with regard to non-linear dynamo models. In the present work, we study the statistical significance of northsouth asymmetry of sunspot areas for the complete solar cycle 23 (1996 - 2008). The dominant hemisphere in each year of the cycle 23 has been identified by calculating the probability of hemispheric distribution of sunspot areas. The statistically significant intermediate-term periodicities of the north-south asymmetry of sunspot area data have also been investigated using wavelet technique. A number of short and mid-term periods are detected and most of them are found to be time variable. We present our results and discuss their possible explanations for different solar mid-term periodicities.

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Keywords : Sun: activity – sunspots