Investigation of a laboratory plasma for a geophysical simulation experiment

Summary form only given. Laboratory experiments and numerical simulations at the University of Strathclyde investigate the phenomenon of Auroral Kilometric Radiation (AKR) which is generated naturally in the polar regions of the Earth´s magnetosphere as electrons descend through regions of plasma depletion, the auroral density cavity, and experience magnetic compression. Satellites have measured values of f_pe~9kHz, n_e~10⁶m^-3 and f_ce~300kHz within the auroral density cavity.The initial AKR simulation experiments did not reproduce the background plasma, therefore experiments have been conducted to create a low density, low temperature discharge to improve comparison between the experiments and the auroral situation. A Penning trap was designed and installed into the interaction region of the experimental apparatus allowing a discharge to be formed in helium at 5x10^-4 mBar. A plasma probe was used to characterize the discharge, estimating f_pe~150-300MHz and nε-10¹⁴-10¹⁵m^-3, whilst the cyclotron frequency of the electrons within the Penning trap was 5.87GHz giving the ratio f_ce/f_pe -19-40, comparable to the magnetospheric case. A Marie-converter, designed at Strathclyde, was used as a test diagnostic for the cathode mesh piece of the Penning trap apparatus. The idea of the cathode mesh, with a spoke wire design, was to allow egress of TE_0m radiation, whilst acting as a reflector of electrons within the trap, therefore containing them to collide and ionize with the background gas. As the Marie-converter was specifically designed to emit TE₀₁ modes, the transmission properties of the Penning cathode mesh could be tested on the converters output.