Observations of energetic ion enhancements and fast neutrals upstream and downstream of Uranus' bow shock by the Voyager 2 spacecraft

The low energy charged particle experiment on Voyager 2 performed measurements of energetic ions and electrons upstream and downstream from the planet Uranus. The results are summarized. Discrete ion increases associated with the bow shock were observed upstream at distances ≤ 140Ru; lower density enhancements may occur as far away as ≥ 500Ru. Downstream ion events occur to distances of ∼ 1500Ru. Ion energy spectra extend to ∼ 1Mev and are similar to those measured inside the planet's magnetopause. Low energy ions exhibit anisotropies and are typically field-aligned. A condition for the appearance of these ions at Voyager is near-connection of the interplanetary field (IMF) to the bow shock. The presence of ions is near-coincident with depression of the IMF magnitude. It is concluded that the upstream events favour leakage from the magnetosphere as the source of particles. (U.K.)