Author
John F. Cooper
Other affiliations: STX Corporation, University of Colorado Boulder
Bio: John F. Cooper is an academic researcher from Goddard Space Flight Center. The author has contributed to research in topics: Solar wind & Cosmic ray. The author has an hindex of 21, co-authored 96 publications receiving 2047 citations. Previous affiliations of John F. Cooper include STX Corporation & University of Colorado Boulder.
Topics: Solar wind, Cosmic ray, Magnetosphere, Ionization, Enceladus
Papers published on a yearly basis
Papers
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TL;DR: Galileo Orbiter measurements of energetic ions (20 keV to 100 MeV) and electrons (20-700 keV) in Jupiter's magnetosphere are used, in conjunction with the JPL electron model (less than 40 MeV), to compute irradiation effects in the surface layers of Europa, Ganymede, and Callisto as mentioned in this paper.
395 citations
TL;DR: In this paper, the authors present model flux spectra derived from spacecraft data and models for eV to GeV protons at 40 AU, a termination shock position at 85 AU, and galactic cosmic ray ions from the Local Interstellar Medium (LISM).
Abstract: Times for accumulation of chemically significant dosages on icy surfaces of Centaur, Kuiper Belt, and Oort Cloud objects from plasma and energetic ions depend on irradiation position within or outside the heliosphere. Principal irradiation components include solar wind plasma ions, pickup ions from solar UV ionization of interstellar neutral gas, energetic ions accelerated by solar and interplanetary shocks, including the putative solar wind termination shock, and galactic cosmic ray ions from the Local Interstellar Medium (LISM). We present model flux spectra derived from spacecraft data and models for eV to GeV protons at 40 AU, a termination shock position at 85 AU, and in the LISM. Times in years to accumulate dosages ~100 eV per molecule are computed from the spectra as functions of sensible surface depth less than one centimeter at unit density. The collisional resurfacing model of Luu and Jewitt is reconsidered in the context of depth-dependent dosage rates from plasma, suprathermal, and higher energy protons, and global exposure, by micrometeoroid dust grain impacts, of moderately irradiated red material below a thin crust of heavily irradiated neutral material. This material should be more visible on dynamically ‘cold’ objects in the ~40 AU region.
142 citations
01 Jan 2004
TL;DR: The surfaces of Jupiter's moons are profoundly weathered by jovian charged particle and solar ultraviolet (UV) irradiation, and it has only recently been shown quantitatively that radiolysis and photolysis, the chemical alteration of a surface by charge-particles and by the solar UV, are in fact occurring on the surfaces of these moons.
Abstract: The surfaces of Jupiter's moons are profoundly weathered by jovian charged particle and solar ultraviolet (UV) irradiation. Although early observations of the Galilean satellites suggested that their reflectance spectra were modified by energetic particles, it has only recently been shown quantitatively that radiolysis and photolysis, the chemical alteration of a surface by charge-particles and by the solar UV, are in fact occurring on the surfaces of these moons.
127 citations
TL;DR: In this article, a model for the toroidal O2 atmosphere indicated by the detection of O 2 + and O 2+ over the main rings was described for the Saturn's magnetosphere.
112 citations
TL;DR: In this paper, a collisional Monte Carlo model of Europa's atmosphere is described, in which the sublimation and sputtering sources of H2O molecules and their molecular fragments are accounted for as well as the radiolytically produced O2.
111 citations
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01 Dec 2007
TL;DR: An estimate of the energy carried by the waves that are spatially resolved indicates that they are too weak to heat the solar corona; however, unresolved Alfvén waves may carry sufficient energy.
Abstract: Alfven waves, transverse incompressible magnetic oscillations, have been proposed as a possible mechanism to heat the Sun's corona to millions of degrees by transporting convective energy from the photosphere into the diffuse corona. We report the detection of Alfven waves in intensity, line-of-sight velocity, and linear polarization images of the solar corona taken using the FeXIII 1074.7-nanometer coronal emission line with the Coronal Multi-Channel Polarimeter (CoMP) instrument at the National Solar Observatory, New Mexico. Ubiquitous upward propagating waves were seen, with phase speeds of 1 to 4 megameters per second and trajectories consistent with the direction of the magnetic field inferred from the linear polarization measurements. An estimate of the energy carried by the waves that we spatially resolved indicates that they are too weak to heat the solar corona; however, unresolved Alfven waves may carry sufficient energy.
562 citations
Book•
01 May 2011TL;DR: In this paper, the authors present an overview of the solar system and its evolution, including the formation and evolution of stars, asteroids, and free-floating planets, as well as their internal and external structures.
Abstract: 1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.
527 citations
University of Nantes1, Imperial College London2, Paris Diderot University3, University of Leicester4, European Space Research and Technology Centre5, University College London6, University of Oxford7, Max Planck Society8, Centre national de la recherche scientifique9, Spanish National Research Council10
TL;DR: The JUpiter ICy moons Explorer (JUICE) mission as mentioned in this paper was selected by ESA in May 2012 to perform detailed investigations of Jupiter and its system in all their interrelations and complexity with particular emphasis on Ganymede as a planetary body and potential habitat.
493 citations
TL;DR: Europa's Plumes Jupiter's moon Europa has a subsurface ocean and a relatively young icy surface, and spectral images taken by the Hubble Space Telescope show ultraviolet emissions from the moon's atmosphere that are consistent with two 200-km-high plumes of water vapor.
Abstract: In November and December 2012 the Hubble Space Telescope (HST) imaged Europa’s ultraviolet emissions in the search for vapor plume activity. We report statistically significant coincident surpluses of hydrogen Lyman-α and oxygen OI130.4 nm emissions above the southern hemisphere in December 2012. These emissions are persistently found in the same area over ~7 hours, suggesting atmospheric inhomogeneity; they are consistent with two 200-km-high plumes of water vapor with line-of-sight column densities of about 1020 m−2. Nondetection in November and in previous HST images from 1999 suggests varying plume activity that might depend on changing surface stresses based on Europa’s orbital phases. The plume was present when Europa was near apocenter and not detected close to its pericenter, in agreement with tidal modeling predictions.
443 citations