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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1263-1279 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transit-time power dissipated locally within a coherent wave packet in the presence of ambient and induced magnetic fields is calculated analytically as a function of position via a perturbed-orbit approach, generalizing earlier results for unmagnetized interactions. The theory is used to investigate local damping in a nonlinearly-collapsing lower-hybrid (LH) wave packet, and hence to estimate the arrest scale of LH wave collapse in a thermal electron-ion plasma. It is shown that either electrons or ions can dominate damping, depending on the strength of the magnetic field and the electron and ion temperatures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1466-1479 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Evolution of waves subject to a randomly varying growth rate is considered and the statistical properties of the waves are calculated in terms of the mean, variance, and correlation time of the growth rate. This enables stochastic growth to be studied without needing full knowledge of the microphysics. However, where the microphysics is understood, this approach also allows it to be easily incorporated into studies of larger-scale phenomena involving stochastic growth. Stochastic differential equations and Fokker–Planck equations are obtained, which describe the wave evolution in the presence of a variety of linear and nonlinear processes and boundary conditions, and it is shown that these phenomena can be diagnosed observationally through their effects on the statistical distribution of the wave field strengths. The results are particularly useful for waves with small dispersion, where they explain the strong wave clumping often observed in nature and emphasize the role of marginal stability in setting the level about which fluctuations occur and in determining their magnitude. Application to type III solar radio bursts illustrates many of the main results and verifies and generalizes earlier conclusions reached using a less rigorous approach. In particular, a new condition for marginally stable propagation of type III solar electron beams is found. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3799-3807 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The three-wave decay of a Langmuir wave into an ion-sound wave and an electromagnetic wave close to the plasma frequency is analyzed. Realistic approximations to the spectra for the Langmuir and ion-sound waves are used to enable analytic calculation of the resulting spectrum of transverse electromagnetic waves in terms of a single well-behaved integral. This integral is approximated analytically and evaluated numerically and the results are compared with each other and with previous estimates. Applications of the results to type III solar radio bursts and laboratory plasmas are also discussed and it is found that the present analytic work is relevant to emission by fast beams in both contexts, provided the plasma temperature is not too high. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1279-1287 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The quadratic response tensor provides a complete description of second-order wave processes in a nonlinear medium. The first exact expression is derived for the quadratic response tensor of a warm collisionless plasma, whose particles have a nonrelativistic Maxwellian velocity distribution. The exact expression is written in terms of a set of generalized plasma dispersion functions which satisfy simple symmetry properties and recursion relations and which can be expressed in terms of the standard nonrelativistic plasma dispersion function. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 30 (1989), S. 2484-2487 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A number of new results involving the functions that determine the emission, dispersion, and absorption of waves in nonrelativistic and weakly relativistic plasmas are presented. These results comprise series, integrals, recursion relations, symmetry properties, interrelations, approximations, and connections with standard transcendental functions.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 525-534 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An investigation is made of the conditions under which the expression for the dielectric tensor from magnetized-plasma theory may be approximated by that from unmagnetized-plasma theory. Surprisingly, the conditions usually quoted are shown to be inaccurate chiefly because they make no reference to the form of the plasma distribution function. Corrected conditions depend strongly on the distribution function and their application is thus highly problem-dependent. For completely arbitrary distributions these conditions are generally stronger than the commonly quoted ones for weakly damped waves. By contrast, the conditions applicable to axisymmetric distributions can be weaker than some of those commonly quoted. A geometric interpretation of the revised conditions for axisymmetric distributions is given in terms of the resonance ellipses of cyclotron maser theory and is illustrated with reference to dispersion and instability of Langmuir and Bernstein waves in weakly magnetized plasmas. These results apply to all weakly magnetized plasmas that can be described by the linearized Vlasov equations and imply that some investigations which have used the commonly quoted conditions to justify use of unmagnetized-plasma theory may be in error on this point.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 107-114 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects on dispersion at perpendicular propagation are found to persist at other angles; these effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 28 (1987), S. 1203-1205 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A number of results are presented involving the plasma dispersion functions appropriate to waves in weakly relativistic, magnetized, thermal plasmas. These results include generating functions, series, integral forms and interrelations, and several useful approximations.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 27 (1986), S. 1206-1214 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The known properties of plasma dispersion functions (PDF's) for waves in weakly relativistic, magnetized, thermal plasmas are reviewed and a large number of new results are presented. The PDF's required for the description of waves with small wave number perpendicular to the magnetic field (Dnestrovskii and Shkarofsky functions) are considered in detail; these functions also arise in certain quantum electrodynamical calculations involving strongly magnetized plasmas. Series, asymptotic series, recursion relations, integral forms, derivatives, differential equations, and approximations for these functions are discussed as are their analytic properties and connections with standard transcendental functions. In addition a more general class of PDF's relevant to waves of arbitrary perpendicular wave number is introduced and a range of properties of these functions are derived.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 490-498 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The existence of two previously unrecognized contributions to transit-time damping in systems of more than one dimension is demonstrated and discussed. It is shown that these contributions cannot be treated by one-dimensional analyses unless it is assumed that the gradient of the field perpendicular to itself always vanishes. Such an assumption is unjustified in general and the new contributions can dominate damping by fast particles in more general situations. Analytic expressions obtained using a Born approximation are found to be in excellent agreement with numerical test-particle calculations of transit-time damping for a variety of field configurations. These configurations include those of a resonance layer and of a spherical wave packet, which approximates a collapsing wave packet in a strongly turbulent plasma. It is found that the fractional power absorption can be strongly enhanced in non-slablike field configurations.
    Type of Medium: Electronic Resource
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