New Supernova Constraints on active-sterile neutrino conversions

We consider active-sterile neutrino conversions in a supernova in the presence of random magnetic field domains. For large enough fields the magnetization of the medium may enhance the active to sterile neutrino conversion rates. Neglecting neutrino transition magnetic moments we show that for KeV neutrino mass squared differences these limits may overcome those that would apply in the isotropic case.