Matter-enhanced spin-flavor precession of solar neutrinos with transition magnetic moments

Experimental and astrophysical limits on the neutrino magnetic moments and the magnetic fields in the solar interior are briefly reviewed. For the case of simultaneous flavor mixing and nonzero transition magnetic moments left-handed electron-neutrino survival probability contours are calculated for Cl and Ga detectors for several possible magnetic-field configurations. A possible explanation of the variation of the solar-neutrino flux with the solar cycle is pointed out. This solution requires a magnetic field in the bottom of the convective zone of the Sun with B∼(1--2)x105 G and a transition magnetic moment of (5--10)x10-12μB