Characteristics of sunward flowing proton and alpha particle fluxes of moderate intensity

The diffusive streaming of 1.3to 2.3-MeV per nucleon protons has been found to be predominantly toward the sun during periods between prompt solar particle events. This sunward streaming occurs for essentially all proton intensities from <0.012 to 1.2 (cm •' s sr MeV) -• and for all solar wind velocities. The average radial component (16% + 3%) of the diffusive anisotropy of 1.4to 2.4-MeV per nucleon alpha particles is very similar to that observed for protons (14% + 1%), a finding suggesting a common origin. These periods are characterized by a limited variance in the proton intensities (10 -1-•'ñ•.1 cm -•' s -• sr -• MeV-•), in the proton spectra (E-3-øñø'8), and in the a/p ratio (3% q2%). The sunward diffusion of protons and alpha particles indicates that a positive radial gradient is characteristic of these modestly enhanced fluxes. A steady state propagation model which includes adiabatic energy loss and a source of particles beyond 1 A U produces the average radial anisotropy and its dependence on the solar wind velocity for Krr • 4 X 10 •'ø cm •' s -•. The direction of the diffusive anisotropy is strongly dependent on the magnetic field direction, a situation indicating K• < •. However, the two directions are not identical, a condition indicating nonnegligible flow perpendicular to the average field direction when averaged over a 6-hour interval.