Low Energy Particles in the Outer Heliosphere Near Solar Minimum

The study of low energy ions in the outer heliosphere has been extended to the near minimum conditions of 1985-1986. Voyager 1 reached a heliographic latitude of 27.3 degrees at 26.5 AU on day 120 of 1986. Voyager 2 was at 20 AU and within 1 degree of the solar equator at the same time. The longitude separation between the spacecraft was less than 30 degrees at that time. Interplanetary shock acceleration events from approximately 40 keV to approximately 1 MeV ions became much less frequent and weaker starting about day 80 of 1985 at both spacecraft despite the approximately 5 AU difference in radial distance. The average flux decreased at all energies with a drop by a factor of approximately 20 at 1 MeV. The decrease to lower levels took approximately 90 days.