Basic Equations

  • A. D. M. Walker
Part of the Physics and Chemistry in Space Planetology book series (SPACE, volume 24)


A plasma is a gas in which a substantial number of the molecules are ionized and show collective behavior. This collective behavior occurs provided that there are a sufficient number of particles within a sphere of radius equal to the Debye length,
$$\lambda _D = (\varepsilon _0 KT/Nq^2 )^{1/2}$$
All symbols are defined in Appendix D. On scales small compared with λD the individual particle behavior is important. On scales larger than λD the Coulomb potential of a single particle is screened by charges of the opposite sign. The unperturbed plasma is electrically neutral over length scales greater than λD. Although neutral, because of the ionization, a plasma is a conductor, and this leads to behavior which is far more complicated than that of an unionized gas. A plasma permeated by a background magnetic field is called a magnetoplasma.


Volume Element Lorentz Force Cold Plasma Velocity Distribution Function Poynting Vector 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1993

Authors and Affiliations

  • A. D. M. Walker
    • 1
  1. 1.Department of PhysicsUniversity of NatalDurbanSouth Africa

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