Energetic particle observations near the termination shock

The most recent data from Voyager 1 (V1) show that a second event (TS2), apparently associated with the termination shock (TS), is in progress, with spectral characteristics similar to the energetic particle increase observed from 2002.4-2003.1 (TS1) [1,2]. We concentrate on the pressure, composition, and anisotropy profiles of TS1. The magnetic field pressure [3] is significantly smaller than the particle pressure perpendicular to the inter-planetary magnetic field (IMF) in the 40-4000 keV range. The composition during the interplanetary shock event (ISE) observed by V1 during 1991 is drastically different from that during TS1 (C/O -0.2 for ISE, similar to0.02 for TS1). The dominant anisotropy during TS1 is azimuthally in the outward direction for a Parker spiral field, suggesting a source inward of the spacecraft, while the radial anisotropy is consistent with zero (-0.024 +/- 0.02), implying a slow (<50 km/s) plasma flow speed. We conclude that the totality of the data is consistent with V1 being in the heliosheath during TS1.