Needed Hot Dark Matter Avoiding the Usual Constraints

While more satellite galaxies continue to be discovered in the Milky Way, ever higher resolution simulations increase the expected number far faster. New physics may be needed to reduce structure on small scales. A possible candidate for this role is hot dark matter in the form of the light sterile neutrino which appears necessary to explain the time variation of solar neutrino fluxes. These variations are found significantly in many solar neutrino experiments with frequencies which are related to rates known from other observations, such as solar rotation frequencies. This sterile neutrino does not mix with active neutrinos, interacting only via a transition magnetic moment. It avoids all the usual neutrino limitations and is produced sufficiently late that it can effect small‐scale, but not large‐scale, structure. The light sterile is produced from the decay of a heavier sterile (∼keV), which similarly interacts only via a transition magnetic moment and is the main component of cold, or possibly warm, dark matter. Such a decay can occur only in the presence of a sufficient magnetic field, so this happens gradually after matter forms. It turns out that DAMA/LIBRA could be observing this decay process.