The majority of navigation satellite receivers operate on a single frequency and experience an error due to the ionospheric delay. They compensate for the ionospheric delay using an ionospheric model which typically only corrects for 50% of the delay. An alternative approach is to map the ionosphere with a network of real-time measurements, with either a thin shell approximation or a full 3D map. Here, a time-dependent 3D tomographic imaging technique is used to map the free electron density over the full-height of the ionosphere during solar maximum. The navigation solutions computed using corrections based upon models and thin-shell and full-height maps are compared in this project. The models and maps are used to calculate the excess propagation delay on the L1 frequency experienced by GPS receivers at selected locations across Europe and North America. The excess delay is applied to correct the pseudo-range single frequency observations at each location and the improvements to the resulting positioning are calculated. It is shown that the thin-shell and full-height maps perform almost as well as a dual-frequency carrier-smoothed benchmark and for most receivers better than the unfiltered dual-frequency benchmark. It is also shown that the unfiltered dual-frequency method is not reliable, which is of concern as it is a proposed upgrade to current positioning systems. The improvements in positioning accuracy vary from day to day depending on ionospheric conditions but can be up to 25m during mid-day at solar maximum conditions at European mid-latitudes. The full-height corrections perform well under all geomagnetic conditions and are considerably better than thin-shell corrections under extreme storm conditions. The transmission of the navigation correction requires a forecast, an image compression and a system of distribution across a local region. The feasibility of this is demonstrated for regions of land and near-land coastal regions across Europe.

The Super Dual Auroral Radar Network (SuperDARN) of HF coherent radars has been originally designed to monitor echoes, and thus study physical processes, from within the auroral oval, the area with the most frequent occurrence of discrete auroras. Monitoring of higher latitudes, the so-called polar cap (including the magnetic Poles areas), was anticipated because of over-the-horizon nature of the radars, but this capability was considered to be a value-added feature. Recently (2006 and 2008), two new radars at Rankin Inlet and Inuvik (Canada) were installed by the University of Saskatchewan radar group to be able to monitor HF echoes from within the polar cap directly. In this Thesis, two aspects of the Rankin Inlet (RKN) radar observations are investigated. First, occurrence of ionospheric echoes is studied. Assessment of the echo occurrence rate is performed and the rate is compared with observations of concurrently operating Saskatoon and Halley (Southern hemisphere) SuperDARN radars. It is shown that the RKN overall occurrence rates (within the optimal area of detection) are ~20% which is well above the rates for the Saskatoon (~6%) and Halley (~1%) radars. The rates are somewhat smaller in the early morning (02-05 MLT) and postnoon (15-20 MLT) hours of magnetic local time. Seasonally, the rates are smaller for summer with significant drop near the magnetic noon. Secondly, an event of the RKN radar monitoring of a polar cap arc, progressing through the radar field of view, is presented. F region echoes are shown to be stronger in the arcs wake, and they are broader on both its sides. Arc-related sheared plasma flows were demonstrated by considering the radar velocity measurements. Occasional occurrence of strong shears away from the arc was noticed, and it was related to the onset of a second, sub-visual arc, emerging from the auroral oval and intruding the polar cap. The data presented demonstrate the usefulness of the RKN observations of the high-latitude arcs whose mechanism of formation is presently unclear. An attempt has been made to discern magnetic signatures of the polar cap arc. Magnetic perturbations were found to be very weak and not easily interpreted.

The Super Dual Auroral Radar Network (SuperDARN) of HF coherent radars has been originally designed to monitor echoes, and thus study physical processes, from within the auroral oval, the area with the most frequent occurrence of discrete auroras. Monitoring of higher latitudes, the so-called polar cap (including the magnetic Poles areas), was anticipated because of over-the-horizon nature of the radars, but this capability was considered to be a value-added feature. Recently (2006 and 2008), two new radars at Rankin Inlet and Inuvik (Canada) were installed by the University of Saskatchewan radar group to be able to monitor HF echoes from within the polar cap directly. In this Thesis, two aspects of the Rankin Inlet (RKN) radar observations are investigated. First, occurrence of ionospheric echoes is studied. Assessment of the echo occurrence rate is performed and the rate is compared with observations of concurrently operating Saskatoon and Halley (Southern hemisphere) SuperDARN radars. It is shown that the RKN overall occurrence rates (within the optimal area of detection) are ~20% which is well above the rates for the Saskatoon (~6%) and Halley (~1%) radars. The rates are somewhat smaller in the early morning (02-05 MLT) and postnoon (15-20 MLT) hours of magnetic local time. Seasonally, the rates are smaller for summer with significant drop near the magnetic noon. Secondly, an event of the RKN radar monitoring of a polar cap arc, progressing through the radar field of view, is presented. F region echoes are shown to be stronger in the arcs wake, and they are broader on both its sides. Arc-related sheared plasma flows were demonstrated by considering the radar velocity measurements. Occasional occurrence of strong shears away from the arc was noticed, and it was related to the onset of a second, sub-visual arc, emerging from the auroral oval and intruding the polar cap. The data presented demonstrate the usefulness of the RKN observations of the high-latitude arcs whose mechanism of formation is presently unclear. An attempt has been made to discern magnetic signatures of the polar cap arc. Magnetic perturbations were found to be very weak and not easily interpreted.

Abstract In this study, we use a fisheye lens (180o field of view) and Chare-Couple Device to take the all-sky 6300Å airglow images emitting from ionosphere. By analyzing these Images we can study the phenomenon of equatorial plasma depletions (plasma bubble). Plasma bubbles generate above the magnetic equator; and they drift up to higher altitude and spread to higher latitude area along magnetic lines. The all-sky imaging system was operated at Mt. A-Li (23.511oN, 120.823oE). Because this year is the most active time of sunspots in the solar cycle, we expect that we can take mounts of plasma bubble images in this year.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 121-129). Available also in a digital version from Dissertation Abstracts.

Thesis--M. Phil., University of Hong Kong, 1981.

Thesis (M. Sc.)--University of Hong Kong, 1967. / Mimeographed.

Thesis--Ph. D., University of Hong Kong. / Mimeographed.

The report contained herein is a statistical analysis of electron temperatures withinTitan’s lower ionosphere. Electron temperatures in this altitudinal range are of greatimport for researchers. The main contributing factors are investigated to see whatphysical processes are the sources of variability in electron temperatures. Oneimportant result from this analysis lends itself to determining recombinationcoefficients thus determining organic process rates occurring within Titan’satmosphere. To accomplish this analysis, data from the Langmuir probe aboard the Cassini craft isutilized. The Langmuir probe is an instrument which can be used to measure currentdifferences in a plasma environment. From this, plasma properties such astemperature, density, and velocity can be calculated. It was named after IrvingLangmuir, whose theories became the basis for Orbit Motion Limited theory. Of the possible factors that determine the variation in electron temperatures, altitudewas the most evident and largest contributor. Once the data had been reduced toremove the effect of altitude on the temperature, other factors such as latitude, solarzenith angle, and ram angle were investigated to ascertain which, if any, wasresponsible for variations in temperature. Upon completion of the analysis, it waslearned that ram angle also had an identifiable effect upon electron temperatures. This effect was further investigated to ensure confidence in the results. Thecompletion of this part of the analysis showed that the effect shown with respect toram angle was indeed reproducible and that no other investigated factor had a majoreffect on electron temperatures. After the confidence procedure was completed,several previous studies findings were confirmed. These confirmed results include therelation of solar zenith angle with respect to both electron temperature distributionand density distribution, as well as a possible confirmation relating temperature anddensity for electrons.n/

127 leaves : ill., appendix / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1973