Local transit-time damping of electrostatic wave packets

Abstract

The theory of local transit-time damping is generalized to coherent electrostatic wave packets with nonzero mean wave number in an unmagnetized plasma. A general analytic formula for the phase-averaged power dissipated locally within an arbitrary three-dimensional wave packet is derived to second order in the fields. This expression is evaluated explicitly for a representative one-dimensional field structure. The result agrees with independent numerical test-particle calculations to within numerical rounding errors for small to moderate field amplitudes, which justify the perturbation expansions. The resulting damping involves both Landau (resonant) and non-Landau (nonresonant) terms, the la..