6533b82dfe1ef96bd129160b

RESEARCH PRODUCT

Nonlinear inverse bremsstrahlung and highly anisotropic electron distributions

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A procedure is proposed to deal with the approximate solution of the kinetic equation for the velocity distribution function of electrons in a fully ionized plasma in the presence of strong, high frequency radiation. The Legendre polynomial expansion is applied after the kinetic equation has been written in an oscillating frame, where some directions are appropriately scaled, with the aim of making approximately isotropic, on the average, distributions that are otherwise anisotropic. The equations are derived for the isotropic part of the electron distribution in the scaled frame and for the scaling factor. The procedure is meant to display its potential in cases where the electron distribution is expected to be highly distorted by the external field. As a case study, a high-Z plasma, ignoring electron-electron collisions, and a linearly polarized laser field are considered. Within the proposed procedure, the existence of self-similar solutions is addressed as well. For small anisotropy, we recover and improve upon a known result. For large anisotropy, a completely different self-similar solution is found, allowing, in a simple way, the study of many plasma properties under conditions in which the laser field strongly alters the electron velocities. In the unscaled laboratory frame any part of the electron distribution is oscillating, anisotropic, and evolving in shape. \textcopyright{} 1996 The American Physical Society.