FLEXIBLE SIMPLE-POLE EXPANSION OF DISTRIBUTION-FUNCTIONS

A method for parametrization and expansion of distribution functions i s presented. The expansion has a finite number of simple poles, which gives efficient numerical calculations and control of all converging m oments. The low velocity region is Maxwell-like and the high-velocity tail follows an inverse power law. The method is applied to Maxwell-li ke distributions with and without suppressed tails. Dispersion relatio ns can be obtained for a wide class of distributions, using building b locks available in any numerical library. Dispersion relations, for or dinary Langmuir waves and for beam-plasma interactions with intermedia te temperature and beam to plasma density ratio, are derived. The Land au damping, obtained in the long wavelength regime; is of the same ord er but smaller than for the generalized Lorentzian distributions, for a given degree in the power law. (C) 1997 American Institute of Physic s.