ENERGY OF WAVES IN A PLASMA

A formula is given for the energy of an arbitrary electrostatic or electromagnetic wave in a plasma which may be magnetized or unmagnetized, collisional or collisionless, and homogeneous or weakly inhomogeneous. The formula relates the energy of the wave to the magnitude of the electric and magnetic fields of the wave and derivatives of the frequency of the wave with respect to wavenumber and plasma parameters. This formula makes it possible to determine the energy of wave from its dispersion relation (and the magnitude of the fields). The derivation rests on a simple invariance property, related to dimensional analysis, of the Fokker-Planck equation, together with well-known results from the theory of dispersive media. © 1979 American Institute of Physics.