ABSTRACT
Matter can enhance neutrino oscillations (increase the mixing parameter sin2 2θ m ). For small mixing angles in vacuum the enhancement displays a resonance behavior in the neutrino energies or the density of the medium. This resonance effect is important for solar neutrinos in a wide range of oscillation parameters Δm 2 = 10-4-10-8 eV2 and sin2 2θ > 10-4. It leads to a strong suppression of the neutrino flux even for small sin2 2θ.
