| This dissertation presents a full-wave, self-consistent numerical model that enables a greater understanding of how an antenna interacts with warm, collisional, magnetized, multi-species plasma. The model focuses primarily on the frequency region around the critical electron resonances for ionospheric plasma conditions. At these resonances, the dielectric representation of the plasma can become complex or negative, and the current distribution strongly deviates from free space. These effects are difficult to model analytically, necessitating the use of numerical techniques. This dissertation develops a Finite Difference Time Domain model that includes the plasma fluid equations along with Maxwell's equations, and incorporates boundary conditions that address the various speeds of energy propagation. A linearized version of the model allows the simulation to run for hundreds of plasma periods. Simulation results show that the self-consistent current distributions differ from those assumed in analytical models. One outcome of this difference in current distributions is a shift of the zero-phase input impedance crossing of the upper hybrid to a lower frequency than predicted by analytic theories. Additional discrepancies in the input impedance between analytical and numerical models appear to be a consequence of more accurately modeling the near and far fields around an antenna. Qualitative comparisons between simulations of dipole and patch antennas in plasma, and experimental observations of ionospheric sounding rockets and laboratory plasma chambers, demonstrate the improved accuracy and flexibility of the numerical model over analytical techniques. This model should enable the use of the input impedance of an antenna in plasma as a more complete diagnostic tool for measuring plasma environment. |
