Electromagnetic Radiation from Beam Driven Electrostatic Instabilities: Investigation using Computer Simulation

Two-dimensional, electromagnetic particle-in-cell simulations [J.P. Verboncoeur \textit{et al.}, Comp. Phys. Comm. \textbf{87}, 199 (1995)] were used to show, that the interaction of an electron beam, formed from electrons accelerated in a cathode sheath, with the background plasma as it travels into a plasma density gradient produces large-amplitude, high-frequency (HF) electric-field oscillations (close to local plasma frequency) spatially localized in the plasma-density-gradient region. The HF oscillations propagate away from the cathode with phase velocity 5x10$^{6}$ m/s. Half-wavelength, HF standing waves have previously been reported in 1-Dim. simulations [H. Gunell \textit{et al}., Phys. Rev. Lett. \textbf{77}, 5059 (1996)]. We plan to use 2-Dim. simulations to investigate lab-observed correlations between spatially localized, HF standing waves and electromagnetic radiation. We are interested in possible space applications.