ON THE GENERATION OF THE LARGE-SCALE AND TURBULENT MAGNETIC-FIELDS INSOLAR-TYPE STARS

It is thought that the large-scale solar-cycle magnetic field is gener ated in a thin region at the interface of the radiative core (RC) and solar convection zone (SCZ). We show that the bulk of the SCZ virogour sly generates a small-scale turbulent magnetic field. Rotation, while not essential, increases the generation rate of this field. Thus, full y convective stars should have significant turbulent magnetic fields g enerated in their lower convection zones. In these stars the absence o f a radiative core, i.e., the absence of a region of weak buoyancy, pr ecludes the generation of a large-scale magnetic field, and as a conse quence the angular momentum loss is reduced. This is, in our opinion, the explanation for the rapid rotation of the M-dwarfs in the Hyades c luster. Adopting the Utrecht's group terminology, we argue that the re sidual chromospheric emission should have three distinctive components : the basal emission, the emission due to the large-scale field, and t he emission due to the turbulent field, with the last component being particularly strong for low mass stars. In the conventional dynamo equ ations, the dynamo frequencies and the propagation of the dynamo wave towards the equator are based on the highly questionable assumption of a constant alpha. Furthermore, meridional motions, a necessary conseq uence of the interaction of rotation with convection, are ignored. In this context we discuss Stenflo's results about the global wave patter n decomposition of the solar magnetic field and conclude that it canno t be interpreted in the framework of the conventional dynamo equations . We discuss solar dynamo theories and argue that the surface layers c ould be essential for the generation of the poloidal field. If this is the case an alpha-effect would not be needed at the RC-SCZ interface (where the toroidal field is generated). The two central problems faci ng solar dynamo theories may the transport of the surface poloidal fie ld to the RC-SCZ interface and the uncertainty about the contributions to the global magnetic field by the small-scale magnetic features.