Observations of energetic ion and electron enhancements upstream and downstream of Uranus' bow shock by the Voyager 2 Spacecraft.

The Low Energy Charged Particle (LECP) experiment on the Voyager 2 spacecraft performed measurements of energetic ions (E sub i >~ 28 KeV) and electrons (E sub e >~ 22 KeV) upstream and downstream from the planet Uranus. The results can be summarized as follows: (i) discrete ion and electron increases were observed upstream of the bow shock at distances <~ 140 R sub U: Lower intensity ion enhancements may be present as far as ~ 800 R sub U upstream from the planet; (ii) ion energy spectra are described well by dj/dE = KE sup (-gamma) with gamma <~ 3 - 4, extend to ~ 1 MeV and are similar to those measured inside the planet's magnetopause; (iii) the low energy (~ 30 KeV) ions exhibit anisotropies >~ 3:1 and are typically field-aligned; (iv) a necessary (but not sufficient) condition for the appearance of these ions at Voyager is near-connection of the interplanetary magnetic field (IMF) to the bow shock; (v) the presence of ions is near-coincident in several cases with a depression of the IMF magnitude, with energy densities in the energetic particles and the magnetic field approximately equal; (vi) ion events appear downstream from the planet, off the dawn bow shock, to distances of ~ 1800 R sub U.