Radiation of electrostatic plasma waves near the lower hybrid frequency

In an investigation of ray velocities (phase velocities in the direction of the group velocity) with an electrostatic dispersion relation in a hot magnetized plasma, the lower hybrid wave and the ion acoustic wave were found to coexist. Using a small launcher in a magnetized plasma near the lower hybrid frequency, we could observe the lower hybrid wave for low neutral-gas pressure [$P\simeq \mathrm{}(1-2)\mathrm{}\times {10}^{-4\mathrm{}}$ Torr] and the ion acoustic wave for high neutral-gas pressure [$P\simeq \mathrm{}(7-8)\mathrm{}\times {10}^{-4\mathrm{}}$ Torr]. The observed phase velocities for three dimensions were found to be in accord with the theoretical ray velocities. The wave fronts of the lower hybrid wave and the ion acoustic wave are parallel and circular to the magnetic field, respectively.