Mathematics – Logic
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...3e..89k&link_type=abstract
Solar Active Regions and 3D Magnetic Structure, 26th meeting of the IAU, Joint Discussion 3, 16-17 August, 2006, Prague, Czech R
Mathematics
Logic
Scientific paper
In the frames of the macroscopic magnetohydrodynamics in the mixing length approach, we investigated the helicity parameter of turbulent convection in the solar convection zone (SCZ) with taking into account the radial inhomogeneity of turbulent pulsations. Allowance for the harp radial gradient in turbulent velocity results in a change of sign of the helicity parameter from positive to negative (in the northern hemisphere) and, as a consequence, in the formation of the negative alpha-effect layer near the bottom of the SCZ (which has thickness about 30,000 - 40,000 km). The mean negative helicity parameter amplitude (averaged over the negative values region) amounts to 2 m/s. Thus, our analytical calculation show that the α-effect is in agreement with a pioneer idea of Yoshimura (1975, ApJS 29, 467) who first had been considered the numerical dynamo model with two layers in which the alpha-effect has opposite signs. It also agrees with the numerical simulations (Glatzmaier 1985, ApJ 291, 300) and Brummell et al. (1998, ApJ 493, 955), and with estimations of the α-effect based on the current helicity calculations (Pevtsov et al. 1994, ApJ 425, L117; Seehafer 1995, A&A 284, 593; Abramenko et al. 1996, SoPh 168, 75; Bao & Zhang 1998, ApJ 496, L43; Kuzanyan et al. 2000, SoPh 191, 231; Zhang et al. 2006, MNRAS 365, 276). When we take into consideration a nega-tive sign of alpha-effect in deep layers, then the physical conditions at mid to low lati-tudes domain (where a radial gradient of angular velocity, derived from recent helioseismological measurements, has positive sign) are favourable for alphaOmega-dynamo waves to propagate toward equator producing the sunspots migration as the solar cycle progresses. Since at high latitudes the radial gradient of angular velocity has opposite sign, then here the excited dynamo waves must move toward the poles.
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