The Solar Wind in the Outer Heliosphere

This paper reviews solar wind observations in the outer heliosphere, concentrating on new developments in the past 3 years. Voyager 2 has detected an increase in speed and decrease in normalized density, consistent with spending more time in the fast polar ow as it moves to higher heliolatitudes. The proton temperatures continue the increase which began at about 35 AU. We describe a new feature rst detected in 1996, speed oscillations with periods of 1-3 days which comprise 10% of the solar wind data. Solar minimum produced a clear signal in the Voyager 2 data, a at plateau in speed coincident with magnetic eld data showing Voyager 2 stayed south of the current sheet. We present a simple model which reproduces the observed speeds at solar minimum. Finally we show that the variation of solar wind pressure over the solar cycle occurs at both high and low heliolatitudes, in both the fast and slow solar wind.