Generation of the Solar Variable Magnetic Field by the Global Migratory Flow

Abstract—

The article shows the dominant role of the global migratory flow (GMF) ${{v}_{{gmf}}} = \left\{ {v_{{gmf}}^{R},v_{{gmf}}^{\theta },v_{{gmf}}^{\varphi }} \right\}$ in the generation of the variable magnetic field of the Sun ($v_{{gmf}}^{R}$, $v_{{gmf}}^{\theta }$, and $v_{{gmf}}^{\varphi }$ are the radial, meridional, and latitudinal GMF velocity components, which correspond to the velocities of the radial flow variation, spatial and temporal variation of the meridional flow, and torsional oscillations). A magnetic vector $H^{*} = \left\{ {{{H}_{\theta }},{{H}_{\varphi }}} \right\}$, which is called a model bipolar group of spots (${{H}_{\theta }}$ and ${{H}_{\varphi }}$ are the meridional and azimuthal components of the variable magnetic field of the Sun), is introduced. As a result of the performed numerical calculations and on the basis of the kinematic dynamo model, a scheme of the latitude–time distribution of relative amplitudes of magnetic components ${{H}_{\theta }}$ and ${{H}_{\varphi }}$ on the surface of the Sun during the 22-year magnetic cycle are constructed. It is found that the relative amplitudes of the meridional and azimuthal variable fields depend on heliolatitude. They have maximum values in the near-equatorial belt and decrease to minimum values in near-polar belts. In the near-equatorial belt, the magnetic sign of the head spot of the model bipolar group of spots coincides with the sign of the radial field in the near-polar belt. This corresponds to the ratio of the observed signs of the bipolar groups of spots and the near-polar field in the Hale magnetic cycle. At the same time, the signs of bipolar groups of spots at high heliolatitudes are in conflict with the Hale–Nicholson law. Obviously, the violation of the polarities of the vector $H{\kern 1pt}^{*}$ can be explained by taking into account the results of simulating the dependence of the constant toroidal magnetic field on the polar angle that we obtained in previous studies. At the same time, the deviation from the Hale–Nicholson law can apparently be related to the polarity of the first high-latitude bipolar groups of spots of the new cycle observed at the end of old cycles.