Magnetic moments of neutrinos: Particle and astrophysical aspects

We discuss some observational consequences of finite values of neutrino magnetic moments and flavor-changing transition moments (which are expected in some extensions of the standard electroweak model). These include effects on solar and supernova neutrino emission, and contributions to the electromagnetic background in galaxies and clusters of galaxies. To avoid conflict with observational data, transition moments (in units of the Bohr magneton) cannot exceed 3×${10}^{\mathrm{-}15}$ for neutrino masses & above 16 eV, and 6×${10}^{\mathrm{-}14}$ for &≤16 eV.