a1 D épartement CPM /PMT, C.N.E.T. Route de Tr égastol, 22 Lannion, France
The experimental modifications of the classical Landau mode (modification of the first pole, and occurrence of a new propagating mode below the plasma frequency) are due to a peculiar distribution function. This distribution function is approximated by a simple model (i.e. a Maxwellian function plus a water-bag function). A numerical calculation with this model gives new dispersion curves, which agree with experiment.
(Received June 09 1972)
(Revised September 25 1972)