Abstract
In a preliminary analysis of the source spectrum of solar protons, we investigate the case in which energy losses of protons in the source are negligible while they are undergoing Fermi-acceleration. A power law in energy is adopted, under the assumption of an acceleration rate proportional to the energy and dependent on the velocity of the protons. The calculated spectra for several sets of accelerating parameters are compared with the experimental spectrum of the solar proton event of January 28, 1967. The results obtained indicate that the theoretical Fermi-curve which approaches best to the experimental curve corresponds to a parameter set at the source with a 0.4 -1 and r 0.4 5 (acceleration efficiency and mean confinement time respectively). These values imply a source region where the strength of the magnetic field is of the order of 500 gauss and the concentration of plasma particles 10^11 - 10^13 cm-3. The initial flux of protons participating into the acceleration stage is predicted as being only a very small fraction (10^-12 - 10^-14) of the local plasma particles.
