Correlation between energetic ion enhancements and heliospheric current sheet crossings in the outer heliosphere

Voyagers 1 and 2 observed highly-variable beams of energetic ions in the foreshock region upstream of the termination shock (TS). At Voyager 2 (V2), the ion intensities are generally not related to the plasma properties. At Voyager 1 (V1), the beams are often coincident with crossings of the heliospheric current sheet (HCS). The V1 intensity peaks occur when the HCS is crossed from negative to positive magnetic polarities and V1 is within a few AU of the TS. Two mechanisms are considered: current sheet drift and streaming of ions from the TS along magnetic field lines which are parallel to the HCS. The current sheet drift hypothesis predicts that enhancements observed at V2 will occur when the HCS is crossed in the opposite direction, from positive to negative magnetic polarity, since V2 is at southern heliolatitudes.