A SOLAR DYNAMO SURFACE-WAVE AT THE INTERFACE BETWEEN CONVECTION AND NONUNIFORM ROTATION

It is inferred from helioseismology that the vertical gradient in the angular velocity is confined to a thin layer in the overshoot region below the convective zone of the Sun, suggesting an azimuthal magnetic field of several kilogauss in that layer. A field of such strength exceeds the equipartition field (4pirho)1/2[upsilon2]1/2 for the convection, so that the eddy diffusivity is very much less than the eta congruent-to 10(12) cm2 s-1 required in conventional dynamo models to obtained the observed dipole mode of operation. This paper points out that the restriction of the shear partial derivative OMEGA/partial derivative r to a region below the convective zone provides the basic mode with a greatly reduced turbulent diffusion coefficient n in the region of strong azimuthal field. The essential point is that the dynamo takes on the character of a surface wave tied to the lower surface z = 0 of the convective zone. Some specific illustrative examples are provided. The last section comments critically on present ignorance of essential dynamo conditions in the Sun. In particular, there is a substantial body of evidence now suggesting, but not clearly defining, a fibril state for the principle flux bundles beneath the surface of the Sun, with fundamental implications for the solar dynamo.