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Published online by Cambridge University Press: 18 July 2013
The α-effect is central to magnetic field generation in αΩ dynamo theory (Parker, 1955), however, it lacked observational and experimental supports over a long term (Sokoloff, 2007). Mirror asymmetries of magnetic field (magnetic helicity) were not observed until the recent 20 years (Seehafer, 1990; Pevtsov et al., 1995, Bao & Zhang, 1998). Later, the advancement in local helioseismology has made possible the measurements of solar subsurface velocity field and the vorticity (or kinetic helicity) as well (Zhao & Kosovichev, 2003). Apparently, frozen flow with the magnetic field in the fluid of high magnetic Reynold number is a necessary condition for the α-effect in the framework of Parker's dynamo model.