Latitude Dependence of Co-Rotating Shock Acceleration in the Outer Heliosphere

Abstract

Energetic particle observations (E_i ≳ 30 keV) have been made in the outer heliosphere (≳ 12 A.U.) by the LECP instruments on the Voyager 1 and Voyager 2 spacecraft. These observations show a definite latitude dependence of the number and intensities of particle enhancements produced by co-rotating interplanetary regions during a lengthy interval (approximately 200 days) in 1983–84 when no energetic solar particle events were observed. The particle enhancements are significantly fewer in number and tend to be less intense at higher (20°–23°) heliolatitudes. The energy spectral shapes of the accelerated particles at the two spacecraft are similar, indicating that the acceleration process is the same at the two latitudes, but less intense at the higher latitudes.