Extension of Dougherty's Model Fokker-Planck Equation for a Plasma.
AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
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Electromagnetic waves can be severely attenuated and suffer distortion as they propagate through partially ionized gases. These facts must be considered in the design of any communication system in which waves must propagate through an intervening plasma medium, such as in reentry communications and ionospheric propagation. In this report, formulas are given that can predict such wave attenuation characteristics more accurately and for a much wider range of plasma conditions than previous theories. The conventional Appleton-Hartree equation used in ionospheric propagation studies gives the index of refraction of a wave traveling through a plasma in a magnetic field in terms of the properties of the plasma. This conventional Appleton-Hartree formula neglects important effects such as the random thermal motion of the particles, which can produce nonlocal effects. Also, the energy dependence of the electron-neutral collision frequency can alter the nature of the wave attenuation process. A generalization of the Appleton-Hartree equation is made to include these effects and to account for the Coulomb forces between charged particles. A kinetic equation is solved which includes the effects of energy-dependent electron-neutral collisions, Coulomb encounters and spatial dispersion. The perturbation method used in solving the kinetic equation assumes that the effects of Coulomb encounters and spatial dispersion are dominant, and electron-neutral collisions are relatively infrequent. Author
- Plasma Physics and Magnetohydrodynamics
- Radiofrequency Wave Propagation