Plasma Observations from Voyager 2

Abstract

Voyager 2 is now beyond 75 AU and observing the descending phase of the solar cycle. Voyager 2 is the spacecraft in the best position to predict the plasma conditions at Voyager 1 (whose plasma instrument failed). We show that some of the Voyager 1 energetic particle events are associated with plasma changes observed at Voyager 2. Voyager currently observes low speeds, near 400 km/s, suggesting coronal hole flow is not observed. Since the latitudinal speed gradient which occurs in the inner heliosphere at solar minimum has not yet dev3eloped, we can use the speed decrease from Earth to Voyager 2 to determine the solar wind slowdown due to interaction with interstellar H and thus the interstellar H density at the termination shock. We find that the observed slowdown implies a larger H density that previous results.

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