Plasma flows in the heliosheath

Voyager 2 is making the first plasma measurements in the heliosheath. The radial flow speeds in the heliosheath vary between 80 and 200 km/s with an average speed of 138 km/s. The flow in the T (azimuthal) direction is fairly constant and averages about 48 km/s; the flow direction is consistent with flow away from the heliospheric nose. Flow in the N (meridional) direction is also away from the nose and averages -14 km/s. These flows suggest that the shock is blunter in the T than in the N direction, so that the heliosphere is wider than it is high. The flow in the RN plane has quasi-periodic oscillation with a period of 110 days and an amplitude of 21 km/s. The oscillation in flow angle is about 6 degrees in the RN plane and 17 degrees in the TN plane and may result from periodic variations of the termination shock normal direction. Citation: Richardson, J. D., E. C. Stone, J. C. Kasper, J. W. Belcher, and R. B. Decker (2009), Plasma flows in the heliosheath, Geophys. Res. Lett., 36, L10102, doi: 10.1029/2009GL038421.