Statistical Properties of Shock-Accelerated Ions in the Outer Heliosphere

Statistical properties of shock-accelerated protons (E>0.5MeV) in the outer heliosphere (>10AU) are reported using data from the LECP instrument on the Voyager 1 and 2 spacecraft. The log of the proton fluxes in this region of the solar system can be characterized by a log-normal distribution. Multiple window frequency analysis techniques show that, for both Voyagers, the power spectra of the fluxes can be expressed as f sup (-2), with considerable low level but significant detail, for periods tau ~ 100 days; for tau >~ 100 days, the spectra are essentially flat. At these heliospheric distances, the spectral variations and shape for tau >~ 60 days are indicative of evolutionary processes at the solar wind source.