Applications Of A Time-Dependent Polar Ionosphere Model For Radio Modification Experiments
dc.contributor.author | Fallen, Christopher Thomas | |
dc.date.accessioned | 2018-08-07T00:00:55Z | |
dc.date.available | 2018-08-07T00:00:55Z | |
dc.date.issued | 2010 | |
dc.identifier.uri | http://hdl.handle.net/11122/9028 | |
dc.description | Dissertation (Ph.D.) University of Alaska Fairbanks, 2010 | |
dc.description.abstract | A time-dependent self-consistent ionosphere model (SLIM) has been developed to study the response of the polar ionosphere to radio modification experiments, similar to those conducted at the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. SCIM solves the ion continuity and momentum equations, coupled with average electron and ion gas energy equations; it is validated by reproducing the diurnal variation of the daytime ionosphere critical frequency, as measured with an ionosonde. Powerful high-frequency (HF) electromagnetic waves can drive naturally occurring electrostatic plasma waves, enhancing the ionospheric reflectivity to ultra-high frequency (UHF) radar near the HF-interaction region as well as heating the electron gas. Measurements made during active experiments are compared with model calculations to clarify fundamental altitude-dependent physical processes governing the vertical composition and temperature of the polar ionosphere. The modular UHF ionosphere radar (MUIR), co-located with HAARP, measured HF-enhanced ion-line (HFIL) reflection height and observed that it ascended above its original altitude after the ionosphere had been HF-heated for several minutes. The HFIL ascent is found to follow from HF-induced depletion of plasma surrounding the F-region peak density layer, due to temperature-enhanced transport of atomic oxygen ions along the geomagnetic field line. The lower F-region and topside ionosphere also respond to HF heating. Model results show that electron temperature increases will lead to suppression of molecular ion recombination rates in the lower F region and enhancements of ambipolar diffusion in the topside ionosphere, resulting in a net enhancement of slant total electron content (TEC); these results have been confirmed by experiment. Additional evidence for the model-predicted topside ionosphere density enhancements via ambipolar diffusion is provided by in-situ measurements of ion density and vertical velocity over HAARP made by a Defense Meteorological Satellite Program (DMSP) satellite. | |
dc.subject | Atmospheric sciences | |
dc.subject | Plasma physics | |
dc.title | Applications Of A Time-Dependent Polar Ionosphere Model For Radio Modification Experiments | |
dc.type | Dissertation | |
dc.type.degree | phd | |
dc.identifier.department | Department of Physics | |
dc.contributor.chair | Watkins, Brenton | |
refterms.dateFOA | 2020-03-06T01:13:43Z |