Implications for the Cosmic Ray Spectrum of a Negative Electron Neutrino   (Mass)^2
  The hypothesis that the electron neutrino is a tachyon with |m|=sqrt(-m^2) = 0.5 eV/c^2 is consistent with certain properties of the cosmic ray spectrum, including: the existence of a change in power law (the "knee") at E = 10^15 eV, the E^-3 power law after the knee, another change in power law (the "ankle") at E = 10^19 eV, the changes in composition above the knee, the change in anisotropy at the knee, and the absence of a GZK cutoff above E = 4 x 10^19 eV. The hypothesis predicts a substantial flux of cosmic ray neutrons in a narrow energy region just above the knee of the spectrum. 
R. Ehrlich, (George Mason University)