Enhanced solar antineutrino flux in random magnetic fields

We discuss the impact of the recent KamLAND constraint on the solar antineutrino flux on the analysis of solar neutrino data in the presence of Majorana neutrino transition magnetic moments and solar magnetic fields. We consider different stationary solar magnetic field models, both regular and random, highlighting the strong enhancement in the antineutrino production rates that characterize turbulent solar magnetic field models. Moreover, we show that for such magnetic fields inside the Sun, one can constrain the intrinsic neutrino magnetic moment down to the level of ${\mu }_{\nu }\lesssim \mathrm{f}\mathrm{e}\mathrm{w}\times {10}^{-12}{\mu }_B$ irrespective of details of the underlying turbulence model. This limit is more stringent than all current experimental sensitivities, and similar to the most stringent bounds obtained from stellar cooling. We also comment on the robustness of this limit and show that at most it might be weakened by 1 order of magnitude, under very unlikely circumstances.