Protons from the Decay of Solar Neutrons and the Properties of the Interplanetary Medium

Abstract

One of the results of the interaction between flare protons and the solar atmosphere is the generation of neutrons, some of which escape to the interplanetary medium and decay there when propagating. We simulate time profiles of the intensity and anisotropy of “secondary” protons produced in the decay of neutrons. These decay protons are characterized by a distributed (in time and space) source of particles rather than an impulse source, which is typical of primary protons from flares. We use the kinetic transport equation, which includes magnetic focusing, adiabatic losses of energy, and pitch-angle diffusion. We pay special attention to the properties of decay protons from flares on the eastern limb and behind it. Measurements of the time profiles of the intensity and anisotropy of protons produced in such flares may yield estimates of the local pitch-angle scattering coefficient (the mean free path) for protons of a certain energy.