Evidence for interplanetary acceleration of nucleons in corotating interaction regions

Simultaneous measurements of protons and helium in the energy range 0.5--2 MeV per nucleon on IMP-8 (at 1 AU) and Pioneer-10 and Pioneer-11 (between 1 and 8 AU) have revealed a correlation which develops beyond approx.2.5 AU between the positions of double peaks in recurring proton intensity increases and the leading and trailing edges of recurring regions of fast solar wind streams and enhanced magnetic field. From these correlations and the study of energy spectra and the proton-to-helium abundance ratios, it is concluded that there is local acceleration of nucleons, probably near the boundary regions where shocks are observed: even of the nucleons are injected initially at the Sun. (AIP)