  The behaviour of the toroidal and meridional components of the solar
large-scale magnetic field and linear Alfven and Rossby waves during solar
activity cycles and bi-annual time periods are theoretically investigated in
this work. We consider the case of periodical velocity shear with bi-annual
oscillation period . The large-scale magnetic field toroidal and meridional
components are obtained as harmonic functions of the time. The sign reversal of
these magnetic field components is studied. The numerical simulations show
that, due to the velocity shear oscillations, the toroidal or meridional
component of the large-scale magnetic field reverses its sign three times in
one of the hemispheres (northern or southern) of the Sun, during the solar
activity cycle 23. According to our results the appearance of velocity shear
oscillations leads to the modulation of the magnetic field 22-year period
oscillations by the bi-annual ones. The presented model is applicable for
investigation of the magnetic field evolution at the base of convection zone as
well as for understanding the magnetic field properties in the upper solar
atmosphere. The excitement of the linear Rossby and Alfven waves in the shear
layer at the base of the convection zone is also considered. The periodical
impulsive growth is characteristic to the energy density of Alfven and Rossby
waves and they propagate as localized in time powerful pulses. Such behavior of
waves well explains mechanisms of the solar flare excitement and activity.
