  The radiative decay of muon-neutrinos in matter with a scheme of
mass-degenerate neutrinos could be the common origin of the appearance of
anti-electron-neutrinos at LSND and the disappearance of muons-neutrinos at
SuperKamiokande. With the decay probability fixed by the LSND signal, the
deficit of atmospheric neutrinos can be satisfactorily reproduced.
