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Diffusion and Resistivity

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Abstract

The infinite, homogeneous plasmas assumed in the previous chapter for the equilibrium conditions are, of course, highly idealized. Any realistic plasma will have a density gradient, and the plasma will tend to diffuse toward regions of low density. The central problem in controlled thermonuclear reactions is to impede the rate of diffusion by using a magnetic field. Before tackling the magnetic field problem, however, we shall consider the case of diffusion in the absence of magnetic fields. A further simplification results if we assume that the plasma is weakly ionized, so that charge particles collide primarily with neutral atoms rather than with one another. The case of a fully ionized plasma is deferred to a later section, since it results in a nonlinear equation for which there are few simple illustrative solutions. In any case, partially ionized gases are not rare: High-pressure arcs and ionospheric plasmas fall into this category, and most of the early work on gas discharges involved fractional ionizations between 10−3 and 10−6, when collisions with neutral atoms are dominant.

Keywords

  • plasmaPlasma
  • Diffusion equationDiffusion Equation
  • Maxwellian distributionMaxwellian Distribution
  • parallelParallel
  • continuityContinuity

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The original version of this chapter was revised. An erratum to this chapter can be found at https://doi.org/10.1007/978-3-319-22309-4_11

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Chen, F.F. (2016). Diffusion and Resistivity. In: Introduction to Plasma Physics and Controlled Fusion. Springer, Cham. https://doi.org/10.1007/978-3-319-22309-4_5

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