COLLISIONLESS FLUID CLOSURE THEORY AND THE PHASE-VELOCITY TRANSFORM

Fluid equations are derived that describe wave-particle resonances, wh ich usually require kinetic theory. The phase velocity transform is in troduced, which decomposes a function of space and time into a sum ove r components with constant phase velocity. This leads to a new techniq ue to solve partial differential equations, similar but not identical to the Radon transform, and produces recursive solutions. This techniq ue is applied to the collisionless drift kinetic equation, to give clo sure of the fluid moment hierarchy. The result is a new term in the hi ghest moment equation that retains many nonlinear wave-particle effect s not before described by fluid equations.