Neutrino conversions in solar random magnetic fields

We consider the effect of a random magnetic field in the convective zone of the Sun superimposed to a regular magnetic field on resonant neutrino spin-flavor oscillations. We argue for the existence of a field of strongly chaotic nature at the bottom of the convective zone. In contrast to previous attempts we employ a model motivated regular magnetic field profile: it is a static field solution to the solar equilibrium hydro-magnetic equations. These solutions have been known for a long time in the literature. We show for the first time that in addition they are twisting solutions. In this scenario electron antineutrinos are produced through cascades like nu(eL) --> nu(mu L) --> <(nu)over tilde>(eR). The detection <(nu)over tilde>(eR) at Earth would be a long-awaited signature of the Majorana nature of the neutrino, The expected signals in the different experiments (SK, GALLEX-SAGE, Homestake) are obtained as a function of the level of noise, regular magnetic field and neutrino mixing parameters. Previous results obtained for small mixing and ad-hoc regular magnetic profiles are reobtained. We confirm the strong suppression for a large part of the parameter space of the <(nu)over tilde>(eR)-flux for high energy boron neutrinos in agreement with present data of the SK experiment, We find that MSW (Mikheyev-Smirnov-Wolfenstein) regions (Delta m(2) similar or equal to 10(-5) eV(2), both small and large mixing solutions) are stable up to very large levels of noise (P = 0.7-0.8) but they are acceptable from the point of view of antineutrino production only for moderate levels of noise (P similar or equal to 0.95). For strong noise and a reasonable regular magnetic field, any parameter region (Delta m(2),sin(2) 2 theta) is excluded. As a consequence, we are allowed to reverse the problem and to put limits on the r.m.s. field strength and transition magnetic moments by demanding a particle physics solution to the SNP in this scenario. (C) 1999 Published by Elsevier Science B.V. All rights reserved.