Showing papers by "John F. Cooper published in 2014"
University College London1, Planetary Science Institute2, European Space Agency3, Queen Mary University of London4, University of Leicester5, Lancaster University6, University of Wisconsin-Madison7, Jet Propulsion Laboratory8, Cornell University9, Centre national de la recherche scientifique10, University of Grenoble11, Rutherford Appleton Laboratory12, Braunschweig University of Technology13, Delft University of Technology14, University of Liège15, Maynooth University16, Johns Hopkins University Applied Physics Laboratory17, University of Orléans18, Max Planck Society19, Goddard Space Flight Center20, National and Kapodistrian University of Athens21, University of California, Berkeley22, Southwest Research Institute23, Imperial College London24, INAF25, University of Oxford26, University of California, Santa Cruz27, University of Colorado Boulder28, University of Idaho29, Tel Aviv University30, Heidelberg University31, University of Liverpool32, University of Iowa33, University of Southampton34, Royal Observatory of Belgium35, University of Stuttgart36, Bundeswehr University Munich37, university of lille38, Institut de Physique du Globe de Paris39, University of Vienna40, Austrian Academy of Sciences41, National University of Ireland42, Space Science Institute43, University of Cologne44, Université de Namur45, University of Reading46, Pierre-and-Marie-Curie University47, University of California, Los Angeles48, University of the Basque Country49, University of Virginia50, Lunar and Planetary Institute51, Academy of Athens52, University of Potsdam53, International Space Science Institute54, University of Nantes55
TL;DR: In this article, the authors describe the science case for an orbital mission to Uranus with an atmospheric entry probe to sample the composition and atmospheric physics in Uranus' atmosphere, and discuss the technical challenges for such a mission.
75 citations
TL;DR: In this paper, it was shown that at low densities necessary to produce the observed IBEX ribbon via the secondary ENA hypothesis, growth rates are highly sensitive to the temperature of the beam and that even very modest temperatures of the ring beam corresponding to beam widths of <1° are sufficient to damp the self-generated waves associated with the ribbon.
Abstract: The "secondary energetic neutral atom (ENA)" hypothesis for the ribbon feature observed by the Interstellar Boundary Explorer (IBEX) posits that the neutral component of the solar wind continues beyond the heliopause and charge exchanges with interstellar ions in the Outer Heliosheath (OHS). This creates pick-up ions that gyrate about the draped interstellar magnetic field (ISMF) lines at pitch angles near 90° on the locus where the ISMF lies tangential to the heliopause and perpendicular to the heliocentric radial direction. This location closely coincides with the location of the ribbon feature according to the prevailing inferences of the ISMF orientation and draping. The locally gyrating ions undergo additional charge exchange and escape as free-flying neutral atoms, many of which travel back toward the inner solar system and are imaged by IBEX as a ribbon tracing out the locus described above. For this mechanism to succeed, the pick-up ions must diffuse in pitch angle slowly enough to permit secondary charge exchange before their pitch angle distribution substantially broadens away from 90°. Previous work using linear Vlasov dispersion analysis of parallel propagating waves has suggested that the ring distribution in the OHS is highly unstable, which, if true, would make the secondary ENA hypothesis incapable of rendering the observed ribbon. In this paper, we extend this earlier work to more realistic ring distribution functions. We find that, at the low densities necessary to produce the observed IBEX ribbon via the secondary ENA hypothesis, growth rates are highly sensitive to the temperature of the beam and that even very modest temperatures of the ring beam corresponding to beam widths of <1° are sufficient to damp the self-generated waves associated with the ring beam. Thus, at least from the perspective of linear Vlasov dispersion analysis of parallel propagating waves, there is no reason to expect that the ring distributions necessary to produce the observed IBEX ENA flux via the secondary ENA hypothesis will be unstable to their own self-generated turbulence.
28 citations
TL;DR: In this article, the authors discussed the global plasma environment of the TA flyby from the perspective of 3D hybrid modeling, where the background, pickup, and ionospheric ions are considered as particles, whereas the electrons are described as a fluid.
6 citations