University of Maryland
Atlantic Building, Room 2400 4:30 PM Monday, December 1, 2008
Coffee, Tea & Snacks 4:15-4:30 PM

Matthew E. Hill
The Johns Hopkins University Applied Physics Laboratory

The New Jovian Magnetotail: Results from New Horizons

Jupiter’s intense magnetic field carves an enormous cavity, the magnetosphere, into the solar wind plasma. This cavity stretches comet-like away from the Sun into a long magnetotail that reaches at least 4.3 AU to Saturn’s obit. Before 2007 when the Pluto-bound New Horizons spacecraft conducted its fortuitous 110 day tour down Jupiter’s magnetotail, the tail was explored by several probes as far as ~200 RJ (Jovian radius, RJ = 71,492 km) down-tail, plus the brief encounter at Saturn. New Horizons drastically expanded the exploration of the magnetotail by making nearly continuous observations out to ~2500 RJ, (1.3 AU). I will report on the plasma and energetic particle observations made with the SWAP (Solar Wind Around Pluto) and PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) instruments (there is no magnetometer), focusing on three results: (1) The SWAP team [McComas et al. 2007] has reported large recurrent (~500 RJ) plasmoids, expanding as they travel down the magnetotail; (2) the PEPSSI team [McNutt et al. 2007; Hill et al., 2008] observed related bursts of particles injected near Jupiter, showing velocity dispersion as they propagate (the events are punctuated by sharp discontinuities resulting from the spacecraft crossing narrow ~1-RJ-sized structures); and (3) composition studies by the PEPSSI team [Haggerty et al. 2008] identify the bursts as having Iogenic/inner magnetospheric composition and observe the gradual entrance of solar wind He into the tail away from the planet.