PROTON AND ELECTRON MEAN FREE PATHS - THE PALMER CONSENSUS REVISITED

We present experimental and theoretical evidence suggesting that the mean free path of cosmic-ray electrons and protons may be fundamentally different at low to intermediate (< 50 MV) rigidities. The experimental evidence is from Helios observations of solar energetic particles, which show that the mean free path of 1.4 MV electrons is often similar to that of 187 MV protons, even though proton mean free paths continue to decrease comparatively rapidly with decreasing rigidity down to the lowest channels (approximately 100 MV) observed. The theoretical evidence is from computations of particle scattering in dynamical magnetic turbulence, which predict that electrons will have a larger mean free path than protons of the same rigidity. In light of these new results, '' consensus '' ideas about cosmic-ray mean free paths may require drastic revision.