Saturn’s largest moon Titan (2575 km radius) is the second largest in the Solar system. Titan is the only known moon with a fully developed nitrogen-rich atmosphere with ionosphere extending to ~2000 km altitude, hosting complex organic chemistry. One of the main scientific interests of Titan’s atmosphere and ionosphere is the striking similarity to current theories of those of Earth ~3.5 billion years ago. The Cassini spacecraft has been in orbit around Saturn since 2004 and carries a wide range of instruments for investigating Titan’s ionosphere, among them the Langmuir probe, a “space weather station”, manufactured and operated by the Swedish Institute of Space Physics, Uppsala. This thesis reviews the first half of the PhD project on the production of pre-biotic molecules in the atmosphere of Titan and early Earth, focusing on the ion densities and dynamics in Titan’s ionosphere derived from the in-situ measurements by the Cassini Langmuir probe. One of the main results is the detection of significant, up to ~2300 cm-3, charge densities of heavy (up to ~13000 amu) negative ions in Titan’s ionosphere below 1400 km altitude. On the nightside of the ionosphere at altitudes below 1200 km, the heavy negative ion charge densities are comparable to the positive ion densities and are in fact the main negative charge carrier, making this region of the ionosphere exhibit properties of dusty plasma. The overall trend is the exponential increasing of the negative ion charge densities towards lower altitudes. Another important result is the detection of ion drifts that between 880-1100 km altitudes in Titan’s ionosphere translate to neutral winds of 0.5-5.5 km/s. Ion drifts define three regions by altitude, the top layer (above ~1600 km altitude) where the ions are frozen into the background magnetic field, the dynamo region (1100 – 1600 km altitudes) where the ions are drifting in partly opposing directions due to ion-neutral collisions in the presence of the magnetic and electric fields and the bottom layer (below 1100 km altitude) of the ionosphere, where the ions are coupled to neutrals by collisions.

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains vii, 99 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 137-140). Also available via the Internet.

Thesis (M.Sc.)--University of Hong Kong, 1968. / Also available in print.

Thesis (M.S. in Physics)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Cleary, David D. ; Davis, D. Scott. "December 1990." Description based on title screen as viewed on April 2, 2010. DTIC Identifier(s): Ionosphere, Ultraviolet Spectroscopy, Interferometer. Author(s) subject terms: Ionosphere, Ultraviolet Spectroscopy, Interferometer. Includes bibliographical references (p. 64-67). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 1992.

The upper atmosphere, a region above ~85 km called the ionosphere and thermosphere, has been studied extensively for over one hundred years. Measurements were often considered in isolation, but today, advances in technology and ground-based distributed arrays have allowed concurrent multi-instruments measurements. In this dissertation, I combine measurements from all-sky imagers (ASIs), coherent scatter radars, incoherent scatter radars (ISRs), and Fabry-Perot interferometers (FPIs). I focus on two phenomena, the midnight temperature maximum (MTM) and equatorial spread F (ESF), using observations from equatorial to mid-latitudes. The spatial characteristics of these phenomena are not fully understood. I combine observations at various latitudes and longitudes to extend MTM detection to mid-latitudes. I present the first simultaneous detections of the MTM at multiple altitudes and latitudes over North America and the first observations below the F-region peak using the Millstone Hill Observatory ISR in a south pointing, low-elevation mode. The MTM can also be observed with an ASI and I present concurrent measurements of the MTM with an ASI and ISR. The Whole Atmosphere Model, a global circulation model, was found to be consistent with these observations. This further verifies that the MTM is partially created by lower atmospheric tides, demonstrating coupling between the lower and upper atmosphere. In addition to the MTM, I investigate different aspects of ESF using ASIs concurrently with other instruments. I compare various scale sizes (sub-meter to kilometers) using coherent scatter radar and an ASI and conclude that the lower hybrid drift instability causes radar echoes to occur preferentially on the western wall of large-scale depletions. The source of day-to-day variability in ESF is not fully known but I show that one driver may be large-scale wave structures (~400 km) that modulate the development of ESF. Finally, I compare concurrent observations of ESF plasma depletions with ASIs at magnetically-conjugate foot points and show how the magnitude and structure of the Earth’s magnetic field is responsible for differences in the morphology and velocity of these depletions. In summary, I have used multi-instrument observations of ESF and the MTM to provide a deeper understanding of the dynamics of the upper atmosphere.

The study of the ionosphere over the sunrise period is necessary for an understanding of the vtiriations in layer structure with time and has been a topic of research of many workers. On the whole these investigations have been restricted to a study of critical frequency variations with relatively short intervals of a few minutes between successive records, of N-h curves deduced from ionograms with long intervals (15 minutes or so) between successive N-h curves or of continuously monitored single frequency reflections. Not one of the three techniques is entirely satisfactory for a detailed study of ionospheric behaviour over sunrise. The first two do not give a sufficiently clear indication of what happens in the initial stages of layer development, while from the third incomplete data is obtained as to what is happening at a specific electron-density level. For this reason a preliminary investigation of the ionosphere over sunrise was made at Rhodes University during August, 1959. The records were obtained at four-and-a-half minute intervals and scaled by the method of KELSO (1952 ). "Many of t he results were inconclusive but it appeared that records would have to be taken at approximately one minute intervals and reduced to N-h curves by a scaling technique which made full allowance for low-level ionization if useful results were to be obtained. An attempt has been made in this thesis to investigate the behaviour of the ionosphere over sunrise more fully than can be done by the three techniques referred to. A number of observed phenomena are also examined. Part I deals with the theoretical background to ionosphere physics in general and describes the equipment, equipment modifications and experimental procedure. Part II presents the results obtained. The records for a largescale travelling disturbance are analysed. Various observed phenomena are described and discussed. A simple method of obtaining production rates from experimental data is described. The implications of the observed variations of production rates with height and time are discussed. Suggestions for further research and improvement of the methods used arc made in Charter 9.

Jupiter, the largest planet in the solar system, is not only an emitter of thermal radiation like any other planet. Jupiter also emits relatively high-intensity non-thermal radiation in two bands, the decimetre wavelength range and the decametre wavelength range (5 MHz< f < 40 MHz). The decimetric radiation is believed to be due to synchrotron radiation of electrons trapped in a kind of Jovian "Van Allen belt". This thesis deals almost exclusively with the decametric radiation. Although the decametric radiation has been observed for 15 years since its discovery by Burke and Franklin in 1955, there is no generally accepted theoretical model of its generation to be found in the literature as yet. This is not surprising, as there are many complex and confusing aspects of the radiation. And since our knowledge of the Jovian ionosphere, magnetosphere and magnetic field is very limited indeed, every theoretical model must be based on some more or less well justified assumptions. It is, however, possible to draw some conclusions from the observed properties of the decimetric and decametric radiation. The radiation in both bands is polarized. It has been shown that at least part of the polarization is an intrinsic property of the radiation source at Jupiter, This indicates the existence of a Jovian magnetic field. The magnitude and shape of the magnetic field, however, is open to discussion, although a dipole field does seem to be a good approximation at least for large distances from Jupiter. Intro. p. 1-2.

[From Introduction, p. 2] The first chapter of this thesis deals with an analysis of F2 critical frequency data first for SANAE and then for eleven other Antarctic and sub-Antarctic stations covering the period 1957 to 1969. This shows certain aspects of the F2 behaviour. Some of the results of this chapter have been reported in a paper by Gledhill and Williams. The two most important mechanisms thought to be responsible for the Antarctic f₀F2 behaviour are incoming corpuscular radiation and horizontal neutral winds. These two mechanisms together with two others (the temperature theory of Torr and Torr and the semi-annual variation of neutral atmospheric density) are discussed in detail in part 2 (Chapters 2 to 4) with a view to discovering which aspects of the f₀F2 behaviour over Antarctica can be explained by each theory. An attempt is made in Part 3 (Chapters 5 and 6) to explain the observed behaviour by solving the continuity equation of the ionosphere for high-latitude stations. Finally, besides the critical frequency, another parameter of importance in explaining the behaviour in the F2 region is the height at which the F2 maximum occurs. This quantity cannot be read directly from an ionogram and it is not an easy quantity to determine. In fact the way in which it is usually obtained is by "scaling" the ionogram in question and converting the virtual heights obtained into real heights. In Part 4 (Chapter 7 and 8) an outline is given of the two computer programs which were written to perform this conversion.