Solar Dynamo Problem

Abstract

The origin of solar magnetic field and the flux tube nature of this field on the smallest observed scales are two key problems in solar magnetohydrodynamics. Despite the sucess of kinematical models based on the turbulent dynamo theory, continuation of thinking on alternative approaches is justified and may be even necessary. One such approach is based on consideration of energy transfer in magnetogasdynamics production of new magnetic fields near the base of the solar convection zone. It turns out that the field produced by a substantial transfer of energy from thr flows will essential be in the form of strong thin flux sheats that may break into clusters of flux tubes similar to those observed on the sun.Quantitative similirity requires nonlinear MHD interactions of flows with amplitudes ~10/sup4/ cm s/sup-1/ on timescale ~10/sup3/s. Such interactions may be provided by azimuthal magnetoacoustic waves at the longitudes where they cross one another. The required wave amplitudes can be provided by a small fraction of the outward energy flux which must be blocked near the base of the convection zone. The resulting phenomenological model of the magnetic cycle provides for (i) two varieties of activity with distributions and phases similar to the XBP and sunspot cycle, (ii) poleward migrations of large scale fields, (iii) long lived coronal hole like magnetic structures during decline of the sunspot cycle and (iv) relations between the decline of each cycle and the amplitude of the suceeding cycle. The basic postulate of this model remains to be established from solutions of MHD equations. However if established, it will provide promising alternative to the turbulent dynamo model