Published online by Cambridge University Press: 13 March 2009
Hamel & Willis (1966) first showed that anisotropy in temperature could be predicted theoretically in the expansion of a spherical source of gas into a vacuum, thus explaining anisotropies observed to occur in rarefied gas jets. Chou & Talbot (1967) carried out numerical calculations based on similai ideas for a plasma consisting of electrons, ions and neutral particles. These showed that the electron temperature remains isotropic, and little anisotropy occurring among the ions within the (rather extensive) calculations. Here, in the first of two papers, an analytic treatment is applied to the expansion of a fully ionized plasma source, with the particles interacting according to the Coulomb law.