General properties of neutrino spin precession in magnetic field and their possible implication for solar neutrinos

We consider the problem of the spin (or spin-flavour) precession of the solar electron neutrinos veL, possessing a nonzero magnetic moment (or transition moment of magnetic dipole type) μν, in the magnetic field B of the sun, including the case when B twists continuously along the neutrino path. A lower bound on the product of μv and the absolute value of the transverse (with respect to the neutrino momentum) component of B, needed to induce a veL-->vR transition with a given probability, vR being a right-handed neutrino, is derived.