title: A nebula of gases from Io surrounding Jupiter.
abstract: Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (au) from the planet. A population of energetic (>30[?]keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms---and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere---were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103[?]km[?]s-1) and hot magnetospheric neutral wind extending more than 0.5[?]au from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a 'nebula' is created that extends outwards over hundreds of jovian radii.
authors.affiliation: Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, Maryland 20723, USA. tom.krimigis@jhuapl.edu
authors.forename: Stamatios M
authors.initials: SM
authors.lastname: Krimigis
authors.forename: Donald G
authors.initials: DG
authors.lastname: Mitchell
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Hamilton
authors.forename: Jannis
authors.initials: J
authors.lastname: Dandouras
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Armstrong
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Bolton
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Cheng
authors.forename: George
authors.initials: G
authors.lastname: Gloeckler
authors.forename: K C
authors.initials: KC
authors.lastname: Hsieh
authors.forename: Edwin P
authors.initials: EP
authors.lastname: Keath
authors.forename: Norbert
authors.initials: N
authors.lastname: Krupp
authors.forename: Andreas
authors.initials: A
authors.lastname: Lagg
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Lanzerotti
authors.forename: Stefano
authors.initials: S
authors.lastname: Livi
authors.forename: Barry H
authors.initials: BH
authors.lastname: Mauk
authors.forename: Richard W
authors.initials: RW
authors.lastname: McEntire
authors.forename: Edmond C
authors.initials: EC
authors.lastname: Roelof
authors.forename: Berend
authors.initials: B
authors.lastname: Wilken
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Williams