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>Theory and experimental evaluation of a consistent steady-state kinetic model for two-dimensional conductive structures in ionospheric plasmas with application to bare electrodynamic tethers in space.
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Theory and experimental evaluation of a consistent steady-state kinetic model for two-dimensional conductive structures in ionospheric plasmas with application to bare electrodynamic tethers in space.
A steady-state kinetic computational model is developed, allowing for self-consistent simulations of collisionless, unmagnetized flowing plasmas in a vast region surrounding any two-dimensional conductive object. An optimization approach is devised based on a stable, noise-robust Tikhonov-regularized Newton method. Dynamic, adaptive, unstructured meshing allows arbitrary geometries and adequate resolution of plasma sheath features. A 1-D cylindrical solver (KiPS-1D) and a full 2-D solver (KiPS-2D) were developed, the latter using coarse-grained parallelism.; This technique is applied to investigate various applications of special and fundamental importance, principally for space plasmas, although not limited as such. This thesis addresses new simulations and experiments relevant to space borne electrodynamic tethers for propellantless propulsion and for the remediation of radiation belts through charge precipitation, as well as to Langmuir probes for plasma diagnostic in flowing plasmas.; Here, the existing set of plasma sheath profiles and current collection characteristics for round cylinders in stationary plasmas is extended to large bias potentials. Interference effects between two parallel cylinders are shown to exist for spacings upward of 20 times the single-cylinder sheath radius, and an optimal spacing equal to the single-cylinder sheath radius maximizes the sheath area, a finding qualitatively supported by our new experimental data on electron-collecting thin slotted tapes. Also, a thin conductive solid tape is shown to have an equal-capacitance circular radius of about 0.29 times its width. Its predicted collected current characteristic as a function of width approximately agrees with experimental measurements. Further, it has a lower current collection capability than the equal-capacitance circular cylinder.; For ion-attracting cylinders, ionospheric plasma representative of an altitude of 1500 km with a flow energy on the order of the thermal energy is shown to cause significant sheath asymmetries, reducing the sheath radius and current collection by about 30%. For electron-attracting cylinders, a mesosonic flow is experimentally shown to significantly enhance electron collection. This cannot be predicted by a collisionless model and may be due to an elongation of the ram-side pre-sheath into a collisional zone for electrons.
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