Abstract:
We model the structure of the 'steady' (slowest varying) part of the sun's internal poloidal magnetic field assuming it to be (for given reasons and in the relevant domain) a current-free field whose field lines 'isorotate' according to the sun's internal rotation given by helioseismology. This part of the field can be described as that of a central dipole and a central hexapole both parallel to the rotation axis and embedded in a uniform external field. The field structure contains a critical surface (running along the base of the convection zone in the low latitudes), where a discontinuity of about 7 nHz per unit flux in the gradient of rotation may be winding a poloidal field into a toroidal field about 2 MG in about 10 exp 5 - 10 exp 9 yr. Small deviations from isorotation indicate presence of MHD perturbations whose latitude structure and time scales may be similar to those dominant in the solar cycle.
