PROTON AND ELECTRON MEAN FREE PATHS - THE PALMER CONSENSUS REVISITED

We present experimental and theoretical evidence suggesting that the m ean free path of cosmic-ray electrons and protons may be fundamentally different at low to intermediate (< 50 MV) rigidities. The experiment al evidence is from Helios observations of solar energetic particles, which show that the mean free path of 1.4 MV electrons is often simila r to that of 187 MV protons, even though proton mean free paths contin ue to decrease comparatively rapidly with decreasing rigidity down to the lowest channels (approximately 100 MV) observed. The theoretical e vidence is from computations of particle scattering in dynamical magne tic turbulence, which predict that electrons will have a larger mean f ree path than protons of the same rigidity. In light of these new resu lts, '' consensus '' ideas about cosmic-ray mean free paths may requir e drastic revision.