Effect of the interplanetary magnetic field on solar neutron-decay protons

Abstract

Upper bounds are placed on both steady-state and pulse (flare) outflow of neutrons above 1 Mev from the sun. The bounds are obtained by assuming that the neutrondecay protons diffuse in the interplanetary magnetic field, in order to calculate the resultant proton fluxes from simple diffusion theory, and then comparing the theoretical fluxes with recent proton observations. Using the Imp 1 proton spectrum (20–75 Mev) it is shown that there could have been no significant contribution to the inner-belt proton population in that energy range by steady neutron outflow in the first half of 1964, and perhaps as far back as 1961. For the same period and energy range it is concluded that there could have been no higher steady outflow from the sun than ∼1022 neutrons sec−1 Mev−1. As opposed to the meaningful upper bounds obtained for steady neutron outflow, it is found that neutron-decay protons are insensitive indicators of the presence of neutrons in solar flares. For instance, on the order of 10% of flare particles at energies 1 to 100 Mev could be neutrons and yet their decay protons would cause only marginally observable modifications of the primary proton flux during the times of diffusion behavior at 1 AU. The same is true at 0.5 and 1.5 AU.