Understanding the heliosphere and its energetic particles

Classes of cosmic ray variations observed by Helios 1 and 2 spacecraft, Pioneer 10 and 11, and Voyager 1 and 2 spacecraft are reviewed as they correspond to classes of interplanetary flows. Topics covered include: (1) corotating flows, corotating Forbush decreases, and 27-day variations; (2) transients and Forbush decreases; (3) systems of transients and long lasting Forbush decreases; and (4) 11-year variations.