Hemispherical Asymmetry of Large Scale Plasma Flows

Large scale plasma flows like differential rotation, and meridional flow play animportant role in driving the solar dynamo process. These flows show spatial andtemporal variations over the solar cycle and are not symmetric across the equator. Weperform a long-term study (17yr) of the hemispherical asymmetry in torsionaloscillation and meridional flow using the velocity data obtained from GlobalOscillation Network Group (GONG) ring diagram analysis. Our results show that thehemispherical asymmetries in near-surface torsional oscillation and meridional floware strongly related to the asymmetry in the sunspot cycle. We observe that thereexists a time delayed correlation (anti-correlation) between the asymmetries intorsional oscillation (meridional flow) and the sunspot cycle, with the asymmetry inthe flows preceding the cycle asymmetry. Our study puts new constraints on dynamomodels of the solar cycle and may help in predicting the hemispherical cycle strength.While improved flow diagnostics and magnetohydrodynamic simulations are neededto understand the physical processes at play.