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  • 1
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    Remote radio observations of solar wind parameters upstream of planetary bow shocks (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Radio emission is frequently produced at twice the electron plasma frequency 2fp in the foreshock region upstream of the terrestrial bow shock. Observations of this emission provide a remote diagnostic of solar wind parameters in the foreshock. Using ISEE-3 radio data, we present the first evidence that the radio intensity is proportional to the kinetic energy flux and to other parameters correlated with solar wind density. We provide a qualitative explanation of this intensity behavior and predict the detection of similar emission at Jupiter by the Ulysses spacecraft.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: In: Solar Wind Seven; Proceedings of the 3rd COSPAR Colloquium, Goslar, Germany, Sept. 16-20, 1991 (A93-33554 13-92); p. 647-650.
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  • 2
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    Statistical acceleration of electrons by lower-hybrid turbulence (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The statistical acceleration of electrons along an ambient magnetic field by large-amplitude lower-hybrid turbulence is discussed. Perturbations driven by a crossfield current and propagating nearly perpendicular to the applied magnetic field are considered. It is assumed that the instability saturates rapidly and that the fluctuating electric field is predominantly electrostatic. If the turbulence is characterized by a spectrum of small parallel wavenumbers, such that the parallel phase velocity of the waves is greater than the electron thermal velocity, then the turbulence can only accelerate electrons moving with large velocities along the magnetic field. The quasi-linear diffusion equation is solved using a Green's function technique, assuming a power law spectral energy density. The time evolution of an initial Maxwellian distribution is given and the time rate of change of the mean electron energy is calculated for various cases.
    Keywords: PLASMA PHYSICS
    Type: Journal of Plasma Physics; 25; June 198
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  • 3
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    Calculation of the spontaneous cyclotron emissivity using the complete relativistic resonance condition (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An expression for the spectral emissivity of spontaneous synchrotron radiation for a plasma which consists of both thermal and suprathermal electron components is derived using the complete relativistic cyclotron resonance condition. The expression is valid over all angles of propagation. The result is applied to the study of the emission of radiation from an energetic population of electrons with a loss-cone distribution in a relatively low-density plasma (i.e., the electron plasma frequency is less than the cyclotron frequency).
    Keywords: PLASMA PHYSICS
    Type: Physics of Fluids (ISSN 0031-9171); 27; 1396-140
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  • 4
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    Induced emission of radiation near 2(omega sub e) by a synchrotron-maser instability (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In the literature, the emission of radiation at 2(omega sub e), where omega sub e denotes the electron plasma frequency, is usually explained as having been produced by the nonlinear interaction of two Langmuir waves via a backscattering process. Since the emission is frequently observed in solar radio bursts, the mechanism has attracted considerable theoretical interest. In the present paper a model is proposed based on a synchrotron-maser instability excited by a hollow beam of moderately relativistic electrons in a plasma, in which the plasma frequency is much higher than the gyrofrequency. An important conclusion is that, as a result of this instability, unpolarized electromagnetic waves with frequencies near 2(omega sub e) may be amplified.
    Keywords: PLASMA PHYSICS
    Type: Physics of Fluids (ISSN 0031-9171); 28; 846-853
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  • 5
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    Instabilities excited by an energetic ion beam and electron temperature anisotropy in tandem mirrors (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Tandem mirrors are magnetic confinement devices, which have the objective to prevent a leaking out of ions in a central (solenoidal) cell at the end. This is accomplished by making use of an electrostatic potential, which is maintained by a denser plasma in mirror end cells. In the Tandem Mirror Experiment (TMX), Correll et al. (1982) have successfully verified the basic concepts involved in the design of the considered device. However, it was also found that the simple tandem mirror could not be easily scaled to a reactor-size device. Approaches for solving the arising problems were studied, taking into account also the utilization of a thermal barrier. In this connection, Winske et al. (1985) studied the nonlinear development of the instability in a finite beta plasma with isotropic electrons. The present investigation is concerned with an extension of the calculations conducted by Winske et al., giving attention to the parameter regime of the TMX. It is found that three instabilities can occur.
    Keywords: PLASMA PHYSICS
    Type: Physics of Fluids (ISSN 0031-9171); 28; 611-619
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  • 6
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    Electron-cyclotron maser instability caused by hot electrons (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The electron-cyclotron maser instability is studied for energetic electrons with a loss-cone distribution. The instability can occur at all angles of propagation for a wide range of parameters. The growth rate is significantly reduced by the presence of a population of cold electrons, and the instability can be suppressed if the density of the cold electrons is sufficiently large and the temperature of the energetic electrons is not too high.
    Keywords: PLASMA PHYSICS
    Type: Physics of Fluids (ISSN 0031-9171); 28; 2751-275
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  • 7
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    Effect of electron thermal anisotropy on the kinetic cross-field streaming instability (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The investigation of the kinetic cross-field streaming instability, motivated by the research of collisionless shock waves and previously studied by Wu et al. (1983), is discussed more fully. Since in the ramp region of a quasi-perpendicular shock electrons can be preferentially heated in the direction transverse to the ambient magnetic field, it is both desirable and necessary to include the effect of the thermal anisotropy on the instability associated with a shock. It is found that Te-perpendicular greater than Te-parallel can significantly enhance the peak growth rate of the cross-field streaming instability when the electron beta is sufficiently high. Furthermore, the present analysis also improves the analytical and numerical solutions previously obtained.
    Keywords: PLASMA PHYSICS
    Type: Journal of Plasma Physics (ISSN 0022-3778); 32; 159-178
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  • 8
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    Excitation of low frequency waves by streaming ions via anomalous cyclotron resonance (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The effect of a small population of streaming ions on low-frequency waves with frequencies below the ion cyclotron frequency is analyzed for three modes of interest: Alfven waves, magnetosonic waves, and ion-cyclotron waves. The instability mechanism is the anomalous cyclotron resonance of the waves with the streaming ions. Conditions for excitation of the three types of waves are derived and expressions for the growth rates are obtained. Excitation of Alfven waves is possible even if the ratio of the densities of the streaming ions to the thermal ions is very small. For magnetosonic waves, excitation can easily occur if waves are propagating parallel or nearly parallel to the ambient magnetic field. As for ion-cyclotron waves, it is found that for the ion-whistler branch the excitation is suppressed over a broader range of wave frequencies than for the fast magnetosonic branch.
    Keywords: PLASMA PHYSICS
    Type: Physics of Fluids; 21; Aug. 197
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  • 9
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    Distribution function of continuously created newborn and pickup ions in outer cometary exospheres (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The time evolution of the distribution function of newborn ions in the solar wind is investigated using a quasi-linear-type diffusion equation. The initial distribution is taken to be a ring beam, which is approximated by delta function in pitch angle and velocity, and it is assumed that the ions are created at a constant rate with a similar distribution. A long-time asymptotic form of ion distribution is obtained, which is a mixture of newborn ions and ions generated throughout the entire process. It is shown that the time asymptotic distribution function exists even in the presence of a continuous ionization process. The stability of the long-time asymptotic distribution was examined for the case of parallel propagation, and the results show that the distribution function can be unstable to low-frequency hydromagnetic waves. The results of the analysis were found to agree with recent satellite observations.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 8685-869
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  • 10
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    Particle tracing in the magnetosphere - New algorithms and results (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A fast and efficient method is employed to trace charged particles through realistic magnetospheric electric and magnetic fields, greatly reducing computer simulation times. The method is applicable for particles having arbitrary charge, energy, or pitch angle but which conserve the first two adiabatic invariants. An efficient method is used to classify drift orbits, which greatly facilitates identification of the last closed drift path or other drift boundaries. The time-independent evolution of the bounce-averaged phase space density along convective drift orbits is calculated. These three tools can be used to quantitatively describe convective evolution of the particle distribution from the tail, an essential step in understanding the production of unstable distributions in the magnetosphere.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 9; p. 767-770.
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