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  • 1
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    Coupled hydromagnetic wave excitation and ion acceleration at interplanetary traveling shocks (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A theory for the self-consistent configuration of upstream hydromagnetic waves, upstream energetic storm particle (ESP) events, and downstream postshock ion enhancements at interplanetary traveling shocks is presented. The observations of upstream ultralow frequency waves and those ESP events and postshock enhancements which exhibit approximately isotropic ion distributions in the solar wind or shock frame are briefly reviewed. The theory of Lee (1982) for application to interplanetary traveling shocks is modified and analytical solutions for the wave spectrum as a function of wavenumber and z are presented along with the ion omnidirectional distribution functions as functions of energy and z for all ion species. The theory quantitatively explaines the observed features of the shock-associted energetic ions and predicts the configuration of upstream hydromagnetic waves.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; Aug. 1
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  • 2
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    Momentum-dependent diffusive particle acceleration in modified shock fronts (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In the presently derived analytic solutions of the steady transport equation for diffusive particle acceleration in a modified, planar shock front having free escape boundaries, the fluid velocity profile through the shock transition decreases monotonically between the upstream and downstream boundaries. The spatial diffusion coefficient's spatial dependence is linked to that of the fluid velocity profile. Attention is given to the solution corresponding to monoenergetic particle injection at the shock front, with free particle escape at finite distances both upstream and downstream of the shock. The accelerated particle spectrum is dominated at high energies by an exponential cutoff, due to the competition between acceleration by the first-order Fermi mechanism and particle loss through the free escape boundaries.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 215; 341-352
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  • 3
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    Particle acceleration and MHD wave excitation upstream of interplanetary shocks (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The theory of diffusive shock acceleration and its application in interplanetary space are reviewed. Special emphasis is placed on the distinction between diffusive and shock-drift shock acceleration, on ion-excitation of MHD waves upstream of the shock and the resulting self-consistent configuration of waves and accelerated ions, and on the mathematical theory of that configuration at quasi-parallel supercritical interplanetary travelling shocks. A comparison of predicted and observed proton anisotropies for the 12 November 1978 event is presented.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 2-3
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  • 4
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    On the passage of radiation through inhomogeneous, moving media. XII - Polarized waves in a plane, sheared medium (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Using the complete set of Maxwell equations, the ray paths and Stokes parameters of a polarized wave are followed which passes through a slab of differentially shearing material of variable refractive index. The polarization state of the signal leaving the top of the slab is related to the polarization state of the initial wave. In general, the two are not the same. These calculations were made to illustrate the point that the polarization properties of observed pulsar signals may be very different from those of the emitted signals due to propagation effects in the differentially shearing magnetospheres that most pulsars are believed to possess. While it is recognized that the precise amount of polarization variations is model dependent, the calculations show that even for simple situations a noticeable polarization variation occurs. Accordingly, the calculations reported here are an educative device: they show that it is, perhaps, unwise to assume that the observed polarization properties of pulsar signals are the same as the emitted signals.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 198; June 1
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  • 5
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    On the passage of radiation through inhomogeneous, moving media. XI - Nonlinear effects on ray paths in the geometrical optics approximation (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Study illustrating how the presence of a high-intensity pulse of radiation can distort its own passage through a plane differentially shearing medium. It is demonstrated that the distortion is a sensitive function of the precise, and detailed, variation of the medium's refractive index by considering a couple of simple examples which are worked out numerically. In view of the high-intensity pulses observed from pulsars (approximately 10 to the 30th ergs per pulse), it is believed that the present calculations are of more than academic interest in helping unravel the fundamental properties of pulse production in, and propagating through, differentially sheared media - such as pulsars' magnetospheres within the so-called speed-of-light circle.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 194; Dec. 1
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  • 6
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    Waves and irregularities in the solar wind (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This review is meant for the nonspecialist who wants a simple physical picture. Some simple calculations are given to show why waves and irregularities in the solar wind are of importance in obtaining a physical understanding of the dynamical processes occurring in the interplanetary medium. The basic physics of various phenomena observed in the heliosphere, resulting because of the presence of waves in the solar wind, is spelled out in some detail. The most fundamental point made in this review is that a considerable body of phenomena occurring in the solar wind are either caused directly or modified significantly by the turbulent waves that are always present in the solar wind.
    Keywords: ASTROPHYSICS
    Type: Reviews of Geophysics and Space Physics; 12; Nov. 197
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  • 7
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    Coupled hydromagnetic wave excitation and ion acceleration upstream of the earth's bow shock (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A self-consistent theory is set forth for the excitation of hydromagnetic waves and the acceleration of 'diffuse' ions upstream of the earth's bow shock in the quasi-equilibrium that results when the solar wind velocity and the interplanetary magnetic field are nearly parallel. For the waves, the quasi-equilibrium derives from a balance between excitation by the ions, which stream relative to the solar wind plasma, and convective loss to the magnetosheath. For the diffuse ions, the quasi-equilibrium derives from a balance between injection at the shock front, confinement to the foreshock by pitch angle scattering on the waves, and acceleration by compression at the shock front. It also results from loss to the magnetosheath, loss due to escape upstream of the foreshock, and loss via diffusion perpendicular to the average magnetic field onto field lines that do not connect to the shock front. Diffusion equations describing the ion transport and wave kinetic equations describing the hydromagnetic wave transport are solved self-consistently to give analytical expressions. These describe (1) the differential wave intensity spectrum as a function of frequency and distance from the bow shock and (2) the ion omnidirectional distribution functions and anisotropies as functions of energy and distance from the bow shock.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 87; July 1
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  • 8
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    Filamentation instability of magnetosonic waves in the solar wind environment (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Intense magnetosonic waves, originally propagating at the right angle with the interplanetary magnetic field, can excite a purely growing mode along the interplanetary magnetic field together with two symmetric magnetosonic sidebands propagating obliquely across the magnetic field. This instability process leads to the filamentation of the magnetosonic pump waves. These two excited magnetosonic sideband modes propagate together perpendicularly across the magnetic field and, meanwhile, form a standing wave pattern along the magnetic field. The thresholds of this filamentation instability can be exceeded in the solar wind environment. It is predicted that the density fluctuations produced by the filamentation instability along the interplanetary magnetic field have wavelengths greater than, at least, a few earth radii. The polarization of the obliquely propagating magnetosonic waves excited by the filamentation instability is determined by the characteristics of the magnetosonic pump waves and the environmental plasmas.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 13387-13
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  • 9
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    Propagation of cosmic-ray nuclei in a diffusing galaxy with convective halo and thin matter disk (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: A diffusion model for cosmic-ray propagation in the galaxy that includes the effects of convection in the halo is presented. Calculations are made for 13 primary and secondary nuclei with rigidities between 1 and 1000 GV using interaction loss rates, secondary production rates, and radioactive decay on the basis of recent new cross-section measurements. It is found that, in order to fit the rather weak radial dependence of cosmic-ray protons derived from gamma-ray data, the radial profile of the cosmic-ray sources must also have a weak radial dependence. It is suggested that convection perpendicular to the disk of the Milky Way Galaxy may not be important even at rigidities less than a few GV. The obtained limits on halo thicknesses are consistent with what can be determined for the distribution of cosmic-ray electrons in the halo based on the distribution of radio synchrotron emission in this and other galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 390; 1 Ma
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  • 10
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    Model structure of a cosmic-ray mediated stellar or solar wind (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: An idealized hydrodynamic model is presented for the mediation of a free-streaming stellar wind by galactic cosmic rays or energetic particles accelerated at the stellar wind termination shock. The spherically-symmetric stellar wind is taken to be cold; the only body force is the cosmic ray pressure gradient. The cosmic rays are treated as a massless fluid with an effective mean diffusion coefficient k proportional to radial distance r. The structure of the governing equations is investigated both analytically and numerically. Solutions for a range of values of k are presented which describe the deceleration of the stellar wind and a transition to nearly incompressible flow and constant cosmic ray pressure at large r. In the limit of small k the transition steepens to a strong stellar wind termination shock. For large k the stellar wind is decelerated gradually with no shock transition. It is argued that the solutions provide a simple model for the mediation of the solar wind by interstellar ions as both pickup ions and the cosmic ray anomalous component which together dominate the pressure of the solar wind at large r.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 194; 1-2
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