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  • 1
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    Substorm associated ion acceleration in the dynamic magnetotail (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Ion acceleration and flux increase associated with substorm energetic particle injections are investigated on the basis of geosynchronous observations and test proton orbits in the dynamic fields of a three dimensional magnetohydrodynamic simulation of neutral line formation and dipolarization in the magnetotail. The energetic particle flux changes obtained from the test particle orbits agree well with observations that demonstrate rapid ion flux increases at energies of above 20 keV. The injection region inferred from the test particles has a sharp earthward boundary and a sharp ragged tailward boundary. The earthward portion of the enhanced ion flux can be traced to the enhanced cross-tail electric field associated with the near-earth x-type neutral line. Due to the rapid earthward motion of accelerated ions away from the neutral line, this boundary is displaced earthward to where the energetic ions become more adiabatic in the stronger dipolar field.
    Keywords: Geophysics
    Type: ; 243-248
    Format: text
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  • 2
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    Parallel electric fields in extragalactic jets - Double layers and anomalous resistivity in symbiotic relationships (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 306; 451-465
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  • 3
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    Spherically symmetric high-velocity plasma expansions into background gases (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Spherically symmetric plasmas with high expansion velocities have been produced by irradiating targets with eight beams from the Helios CO2 laser in the presence of gases at various pressures. Attention was given to the properties of the target-emitted ions in order to obtain information about the ion-acceleration mechanisms in plasma expansions. Photoionization of the ambient gases by the soft X-ray emission from the laser-irradiated targets produced background plasmas, permitting plasma counterstreaming experiments to be performed in spherical geometry. Successful laser-target coupling in the presence of back-ground gases is obtained; modification of the ion acceleration in accordance with isothermal-expansion models is observed; and an absence of collective coupling between collisionless counterstreaming plasmas is found.
    Keywords: PLASMA PHYSICS
    Type: Journal of Plasma Physics (ISSN 0022-3778); 35; 239-256
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  • 4
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    The theory of Langmuir probes in strong electrostatic potential structures (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The operation of collecting and emitting Langmuir probes and double probes within time-stationary strong electrostatic potential structures is analyzed. The cross sections of spherical and cylindrical probes to charged particles within the structures are presented and used to obtain the current-voltage characteristics of idealized probes. The acquisition of plasma parameters from these characteristics is outlined, and the operation of idealized floating double-probe systems is analyzed. Probe surface effects are added to the idealized theory, and some surface effects pertinent to spacecraft probes are quantified. Magnetic field effects on idealized probes are examined, and the time required for floating probes to change their potentials by collecting charge and by emitting photoelectrons is discussed. Calculations on the space-charge effects of probe-perturbed beams and on the space-charge limiting of electron emission are given in an appendix.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Physics of Fluids (ISSN 0031-9171); 29; 718-730
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  • 5
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    A study of the stochastic energization of charged particles with and without synchrotron energy loss (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A momentum-diffusion formulation that takes the initial values of the particle distribution functions and momentum-space boundary conditions is presently employed for the computational and analytical study of the stochastic energization of charged particles by plasma waves. The nature of the particle distribution functions resulting from stochastic energization and the validity of the momentum-diffusion formulation for the energization are determined. The validity of the momentum-diffusion formulation with power law diffusion coefficients is assessed.
    Keywords: PLASMA PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 308; 929-953
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  • 6
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    Radio-interferometric imaging of the subsurface emissions from the planet Mercury (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The distribution of total and polarized intensities from Mercury's subsurface layers have been mapped using VLA observations. The first detection of a hot pole along the Hermean equator is reported and modeled as black-body reradiation from preferential diurnal heating. These observations appear to rule out any internal sources of heat within Mercury. Polarized emission from the limb of the planet is also found, and is understood in terms of the dielectric properties of the Hermean surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 329; 224-226
    Format: text
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  • 7
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    The laboratory simulation of unmagnetized supernova remnants Absence of a blast wave (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Supernova remnants are experimentally simulated by irradiating spherical targets with eight-beam carbon dioxide laser in a chamber containing finite amounts of neutral gas, the gas being ionized by radiation from the hot target. The expansion velocities of the target plasmas are approximately the same as the expansion velocities of supernova ejecta and the experiment is successfully scaled to the case of a supernova remnant in an unmagnetized, low-density, interstellar medium. No sweep-up of the ambient plasma is detected, indicating that no hydrodynamic shock wave is formed to couple the target ejecta to the ambient gas. The experiment implies that if supernova ejecta couple to the interstellar medium, magnetic-field effects may be crucial to the physical description.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 802-808
    Format: text
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  • 8
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    Numerically simulated two-dimensional auroral double layers (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A magnetized 2 1/2-dimensional particle-in-cell system which is periodic in one direction and bounded by reservoirs of Maxwellian plasma in the other is used to numerically simulate electrostatic plasma double layers. For the cases of both oblique and two-dimensional double layers, the present results indicate periodic instability, Debye length rather than gyroradii scaling, and low frequency electrostatic turbulence together with electron beam-excited electrostatatic electron-cyclotron waves. Estimates are given for the thickness of auroral doule layers, as well as the separations within multiple auroral arcs. Attention is given to the temporal modulation of accelerated beams, and the possibilities for ion precipitation and ion conic production by the double layer are hypothesized. Simulations which include the atmospheric backscattering of electrons imply the action of an ionospheric sheath which accelerates ionospheric ions upward.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 88; Apr. 1
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  • 9
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    Magnetic pumping of particles in the outer Jovian magnetosphere (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The mechanism of magnetic pumping consists of two processes, the adiabatic motion of charged particles in a time-varying magnetic field and their pitch angle diffusion. The result is a systematic increase in the energy of charged particles trapped in mirror (and particularly, magnetospheric) magnetic fields. A numerical model of the mechanism is constructed, compared with analytic theory where possible, and, is used to predict the consequences of the process for cases that are not tractable by analytical means. The model is applied to the outer Jovian magnetosphere for two purposes; to find magnetospheric regions in which the mechanism may energize trapped particles, and to generate distribution functions involving pitch angle diffusion caused by wave-particle interactions. Beyond 20 Jupiter radii in the outer magnetosphere particles may be magnetically pumped to energies of the order of 1-2 MeV and two-temperature distribution functions with 'break points' at 1-4 keV for electrons and 8-35 keV for ions are predicted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; May 1
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  • 10
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    Particle energization in the inner, nonazimuthally symmetric magnetospheres of neutron stars (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The energization process of magnetic pumping, a combination of time dependent magnetic mirror fields with pitch-angle scattering, is applied to trapped charged particles drifting in corotating, azimuthally nonsymmetric neutron star magnetospheres. When particle energization is balanced by synchrotron radiation loss, it is found that protons, rather than electrons, reach considerable kinetic energies and radiate, in the X-ray regime, at rates up to the 10 to the 6th power MeV/proton/sec.
    Keywords: SPACE RADIATION
    Type: NASA-CR-163021 , REPT-80-6
    Format: application/pdf
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