The behaviour of the toroidal and meridional components of the solarlarge-scale magnetic field and linear Alfven and Rossby waves during solaractivity cycles and bi-annual time periods are theoretically investigated inthis work. We consider the case of periodical velocity shear with bi-annualoscillation period . The large-scale magnetic field toroidal and meridionalcomponents are obtained as harmonic functions of the time. The sign reversal ofthese magnetic field components is studied. The numerical simulations showthat, due to the velocity shear oscillations, the toroidal or meridionalcomponent of the large-scale magnetic field reverses its sign three times inone of the hemispheres (northern or southern) of the Sun, during the solaractivity cycle 23. According to our results the appearance of velocity shearoscillations leads to the modulation of the magnetic field 22-year periodoscillations by the bi-annual ones. The presented model is applicable forinvestigation of the magnetic field evolution at the base of convection zone aswell as for understanding the magnetic field properties in the upper solaratmosphere. The excitement of the linear Rossby and Alfven waves in the shearlayer at the base of the convection zone is also considered. The periodicalimpulsive growth is characteristic to the energy density of Alfven and Rossbywaves and they propagate as localized in time powerful pulses. Such behavior ofwaves well explains mechanisms of the solar flare excitement and activity.
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