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We analyse the topology of photospheric magnetic fields and sub-photosphericflows of several active regions (ARs) that are observed during the peak todescending phase of the solar cycle 23. Our analysis shows clear evidence ofhemispheric preferences in all the topological parameters such as the magnetic,current and kinetic helicities, and the 'curl-divergence'. We found that68\%(67\%) ARs in the northern (southern) hemisphere with negative (positive)magnetic helicities. Same hemispheric preference sign is found for the currenthelicities in 68\%(68\%) ARs. The hemispheric preferences are found to existstatistically for all the time except in few ARs observed during the peak andthe end phases of the solar cycle. This means that magnetic fields aredominantly left(right)-helical in scales smaller than individual ARs ofnorthern(southern) hemisphere. We found that magnetic and current helicitiesparameters show equator-ward propagation similar to the sunspot cycle. Thekinetic helicity showed similar hemispheric trend to that of magnetic andcurrent helicity parameters. There are 65\%(56\%) ARs with negative (positive)kinetic helicity as well as divergence-curl, at the depth of 2.4\,Mm, in thenorthern (southern) hemisphere. The hemispheric distribution of the kinetichelicity becomes more evident at larger depths, e.g., 69\%(67\%) at the depthof 12.6\,Mm. Similar hemispheric trend of kinetic helicity to that of thecurrent helicity supports the mean field dynamo model. We also found that thehemispheric distribution of all the parameters increases with the fieldstrength of ARs. The topology of photospheric magnetic fields and near surfacesub-photospheric flow fields did not show good association but the correlationbetween them enhances with depths which could be indicating more aligned flowsat deeper layers of ARs.

Magnetic and Velocity Field Topology in Active Regions of Descending Phase of the Solar Cycle 23