It is shown that the multiple water-bag model, with both analytic and numerical properties, is fairly well suited to the study of forced oscillations launched by grid systems, for different geometries with possible non-uniform charge distribution, and for any distance within the range 0–100 Debye lengths.
Freeston (1968) and Freeston & Malik (1971) compared measurements precisely with theoretical values of the electric field near a system of grids and antennas immersed in a plasma. Results provided a valuable diagnostic tool in space research; and radio-frequency probing was used successfully (Beghin & Debrie 1972; Chasseriaux, Debrie & Renard 1972).