[11] 212 leaves : ill., plates ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1974) from the Dept. of Physics, University of Adelaide

This thesis describes the application of tilting-filter photometry to the study of the airglow and aurora. Previous South African photometric research is reviewed. Optical instrumentation and techniques used in airglow and auroral research are reviewed. The transmission characteristics of narrowband interference filters are discussed. The analogue meridian-scanning tilting-filter photometry system used at Sanae, Antarctica is described. Shortcomings of this system have been identified, and modifications have been made to improve its spatial and temporal resolution. Details are given of the computer-controlled digital photometry system which replaced the analogue system. Equations are derived for the conversion of raw photometric data (analogue chart deflections or digital photon counts) to absolute emission intensities. The accuracy of the intensities obtained depends on the absolute calibration of the photometer, the transmission characteristics of the filter used to isolate the spectral feature of interest, and the effects of atmospheric extinction and scattering. The influence of these factors on observed emission intensities is discussed. Various models used to determine atmospheric correction factors are reviewed. It is shown that atmospheric correction factors can have a significant effect on both emission intensities and intensity ratios. The procedure used to determine the transmission characteristics of interference filters is described, as is the procedure used to cross-calibrate secondary light sources. The transmission characteristics of the filters and the brightnesses of the light sources were both found to have changed appreciably with age. The observation of a magnetospheric substorm at Sanae (L ≃ 4) is used to illustrate the use of a meridian-scanning tilting-filter photometer system in auroral research. The ratio I(557.7)/ I(391.4) observed at Sanae was found to be lower than expected, as were the OJ airglow emission intensities. A prototype digital photometer system was used aboard a ship, to observe the airglow in the region of the South Atlantic Anomaly. Significant N₂⁺ lNG emissions at 391.4 nm were measured, confirming the presence of discernable particle precipitation in the region. The 0I557.7 and 630.0 nm intensities measured from the ship were found to be lower than expected. This, combined with low airglow and auroral intensities measured at Sanae, is a cause for concern. It is recommended that further checks be made regarding the brightness of the calibration sources.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20186号 / 理博第4271号 / 新制||理||1614(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 齊藤 昭則, 教授 田口 聡, 教授 塩谷 雅人 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Ultraviolet (UV) spectra obtained from Earth’s dayglow contain important information for understanding the thermosphere, and the N2 Lyman-Birge-Hopfield (LBH) bands are possibly the most useful emission. To be useful, a thorough understanding of how the LBH band emission varies with altitude and latitude is essential to present and future use of this emission by space-based remote sensors. Excited by photoelectron impact on N2 leading to transitions from the a 1Πg state to the ground state, the LBH emissions radiate between 1270 and 2400 Å. In addition to being populated by electron impact excitation, the a 1Πg state is populated by radiative and collisional cascading from adjacent singlet states a’ 1Σ−u, and w 1∆u (Eastes, 2000). Ultimately, the intensity is most dependent on low energy electron flux (Ajello and Shemansky, 1985; Meier, 1991) because that is where the electron impact scattering cross sections of the singlet states are the largest. This dissertation presents modeled LBH profiles produced using the Intrasystem Cascade Excitation (ICE) model (Eastes, 2000) with photoelectron fluxes calculated using the Continuous Slowing Down (CSD) model (Jasperse, 1976). Both of these models implement the Mass Spectrometer and Incoherent Scatter (MSIS) to model an atmosphere. Modeled emissions are compared against observations by the High resolution Ionospheric and Thermospheric Spectrograph (HITS) on the Advanced Research and Global Observation Satellite (ARGOS). This dissertation will investigate the LBH emissions in detail and ultimately use them for remote sensing of thermospheric temperatures.

<p>The Auroral Large Imaging System (ALIS) was proposed in 1989 by Åke Steen as a joint Scandinavian ground-based nework of automated auroral imaging stations. The primary scientic objective was in the field of auroral physics, but it was soon realised that ALIS could be used in other fields, for example, studies of Polar Stratospheric Clouds (PSC), meteors, as well as other atmospheric phenomena.</p><p>This report describes the design, operation and scientic results from a Swedish prototype of ALIS consisting of six unmanned remote-controlled stations located in a grid of about 50 km in northern Sweden. Each station is equipped with a sensitive high-resolution (1024 x 1024 pixels) unintensified monochromatic CCDimager. A six-position filter-wheel for narrow-band interference filters facilitates absolute spectroscopic measurements of, for example, auroral and airglow emissions. Overlapping fields-of-view resulting from the station baseline of about 50 km combined with the station field-of-view of 50° to 60°, enable triangulation as well as tomographic methods to be employed for obtaining altitude information of the observed phenomena.</p><p>ALIS was probably one of the first instruments to take advantage of unintensi- fied (i.e. no image-intensifier) scientific-grade CCDs as detectors for spectroscopic imaging studies with multiple stations of faint phenomena such as aurora, airglow, etc. This makes absolute calibration a task that is as important as it is dificult.</p><p>Although ALIS was primarily designed for auroral studies, the majority of the scientific results so far have, quite unexpectedly, been obtained from observations of HF pump-enhanced airglow (recently renamed Radio-Induced Aurora). ALIS made the first unambiguous observation of this phenomena at high-latitudes and the first tomography-like inversion of height profiles of the airglow regions. The scientific results so far include tomographic estimates of the auroral electron spectra, coordinated observations with satellite and radar, as well as studies of polar stratospheric clouds. An ALIS imager also participated in a joint project that produced the first ground-based daytime auroral images. Recently ALIS made spectroscopic observations of a Leonid meteor-trail and preliminary analysis indicates the possible detection of water in the Leonid.</p>

The Auroral Large Imaging System (ALIS) was proposed in 1989 by Åke Steen as a joint Scandinavian ground-based nework of automated auroral imaging stations. The primary scientic objective was in the field of auroral physics, but it was soon realised that ALIS could be used in other fields, for example, studies of Polar Stratospheric Clouds (PSC), meteors, as well as other atmospheric phenomena. This report describes the design, operation and scientic results from a Swedish prototype of ALIS consisting of six unmanned remote-controlled stations located in a grid of about 50 km in northern Sweden. Each station is equipped with a sensitive high-resolution (1024 x 1024 pixels) unintensified monochromatic CCDimager. A six-position filter-wheel for narrow-band interference filters facilitates absolute spectroscopic measurements of, for example, auroral and airglow emissions. Overlapping fields-of-view resulting from the station baseline of about 50 km combined with the station field-of-view of 50° to 60°, enable triangulation as well as tomographic methods to be employed for obtaining altitude information of the observed phenomena. ALIS was probably one of the first instruments to take advantage of unintensi- fied (i.e. no image-intensifier) scientific-grade CCDs as detectors for spectroscopic imaging studies with multiple stations of faint phenomena such as aurora, airglow, etc. This makes absolute calibration a task that is as important as it is dificult. Although ALIS was primarily designed for auroral studies, the majority of the scientific results so far have, quite unexpectedly, been obtained from observations of HF pump-enhanced airglow (recently renamed Radio-Induced Aurora). ALIS made the first unambiguous observation of this phenomena at high-latitudes and the first tomography-like inversion of height profiles of the airglow regions. The scientific results so far include tomographic estimates of the auroral electron spectra, coordinated observations with satellite and radar, as well as studies of polar stratospheric clouds. An ALIS imager also participated in a joint project that produced the first ground-based daytime auroral images. Recently ALIS made spectroscopic observations of a Leonid meteor-trail and preliminary analysis indicates the possible detection of water in the Leonid.

The Earth's equatorial ionosphere most often shows the occurrence of large plasma density and velocity fluctuations with a broad range of scale sizes and amplitudes. These night time ionospheric irregularities in the F-region are commonly referred to as equatorial spread F (ESF) or plasma bubbles (EPBs). This dissertation focuses on analysis of ground-based optical and radar measurements to investigate the development and dynamics of ESF, which can significantly disrupt radio communication and GPS navigation systems. OI (630.0 nm) airglow image data were obtained by the Utah State University all-sky CCD camera, primarily during the equinox period, from three different longitudinal sectors under similar solar flux conditions: Christmas Island in the Central Pacific Ocean, Ascension Island in South Atlantic, and Brasilia and Cariri in Brazil. Well-defined magnetic field-aligned depletions were observed from each of these sites enabling detailed measurements of their morphology and dynamics. These data have also been used to investigate day-to-day and longitudinal variations in the evolution and distribution of the plasma bubbles, and their nocturnal zonal drift velocities. In particular, comparative optical measurements at different longitudinal sectors illustrated interesting findings. During the post midnight period, the data from Christmas Island consistently showed nearly constant eastward bubble velocity at a much higher value (~80 m/s) than expected, while data from Ascension Island exhibited a most unusual shear motion of the bubble structure, up to 55 m/s, on one occasion with westward drift at low latitude and eastward at higher latitudes, evident within the field of view of the camera. In addition, long-term radar observations during 1996-2006 from Jicamarca, Peru have been used to study the climatology of post-sunset ESF irregularities. Results showed that the spread F onset times did not change much with solar flux and that their onset heights increased linearly from solar minimum to solar maximum. On average, radar plume onset occurred earlier with increasing solar flux, and plume onset and peak altitudes increased with solar activity. The F-region upward drift velocities that precede spread F onset increased from solar minimum to solar maximum, and were approximately proportional to the maximum prereversal drift peak velocities.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 86-97).

This thesis describes the development, modification and refinement of a high-powered hybrid Stratospheric Tropospheric (ST)/meteor radar at the University of Adelaide’s Buckland Park (BP) field station. This thesis also describes the process of statistically comparing results obtained from multiple co-located independent measurement sources. Also included are statistical comparisons made between meteor radars at BP,Darwin, Northern Territory, and Davis Station, Antarctica, with other independent sources of measurement. Previous meteor radar systems have generally been low powered (∼8 kW peak) and as such could only afford low count rates at frequencies of the order of 50 MHz. While it has been shown that the echo detection rate is inversely proportional to frequency to the power of 1.5, the use of lower VHF frequencies within Australia is restricted by government regulations. As such, this has lead to the development of a high powered meteor radar system at 55 MHz which has served to facilitate higher echo rates at this frequency. The aim of improving the echo rate is to improve the statistical accuracy of results generated by the meteor technique. Also presented are descriptions of the meteor radar systems used to provide the data for this study and the basic principles of the meteor technique. Basic descriptions of the other systems and the techniques used to provide data for comparison are also presented. Two key components in the development of the high-powered meteor system are the high-powered all-sky crossed-dipole transmit antenna and the high-powered 1:2 splitter-combiner required to drive the antenna. The antenna was designed using standard equations for Yagi-Uda antenna design found in literature and modeled using the EZNEC modeling programe. After successful modeling, the antenna was prototyped and refined into a low powered version to investigate the antenna’s performance characteristics. Once the performance of the antenna was verified, the process of upgrading the antenna to handle the full output power from a VTX transmitter was performed. This upgrade also spawned the design and development of the highpowered 1:2 splitter-combiner which would be used to feed the high-powered version of the antenna. The successful operation of the high-powered system over several periods of observation has allowed for a more in-depth investigation into the statistical reliability of the meteor technique. Along with the comparison of standard atmospheric parameters, i.e. temperatures and wind velocity, the high-powered system has allowed for the verification of the relationship between echo rate and radar parameters found by McKinley, which is frequently referred to in many papers dealing with meteor observations. Along with the comparisons made with the results from the high-powered meteor radar system at BP, comparisons of atmospheric parameters derived from meteor observations and other techniques were made at Davis Station and Darwin. Of particular interest is the unique comparison of atmospheric winds made at Davis between two independent meteor radar systems and a Medium Frequency (MF) radar. Previous comparison studies have only enjoyed the benefit of having two independent sources of measurement to compare and as such have not allowed for a unique solution to be obtained for the uncertainties of the techniques using the method of Hocking et al. [2001]. Davis Station is unique in that it has two independent meteor radars in addition to a MF radar. This has enabled for the reduction in the number of degrees of freedom in the statistical comparison process, and as such has allowed for unique solutions to be determined for the uncertainties when comparing two independent techniques; i.e. meteor and MF wind comparisons. Atmospheric temperatures in the Mesospheric and Lower Thermospheric (MLT) region were determined through the use of meteor diffusion coefficients and derived atmospheric pressure models at Davis Station, BP and Darwin. Comparisons are made between the meteor technique and other co-located independent measurements. These include; airglow, satellite and falling sphere measurements at Davis Station, airglow and two independent satellite measurements at BP and two independent satellite observations at Darwin. This thesis as a whole demonstrates the successful operation of the highpowered ST/meteor hybrid radar at BP. It also demonstrates the successful comparisons of MLT winds and temperatures made between meteor radar and other independent sources of MLT measurements. The validation of using the high-powered meteor radar at BP coupled with the successful comparison of atmospheric parameters derived using the meteor technique and other forms of MLT observations serves to re-affirm the statistical accuracy and benefit of the meteor technique in observations of the MLT region. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1474902 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2010

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2017-11-14T13:00:58Z No. of bitstreams: 1 PDF - Bismark Abeku Nyamekye Kushiator.pdf: 1029542 bytes, checksum: 85fec38cb146fdae2ce891a5cb865616 (MD5) / Made available in DSpace on 2017-11-14T13:00:58Z (GMT). No. of bitstreams: 1 PDF - Bismark Abeku Nyamekye Kushiator.pdf: 1029542 bytes, checksum: 85fec38cb146fdae2ce891a5cb865616 (MD5) Previous issue date: 2017-05-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Atmospheric airglow measurements obtained by means of a multichannel photometer in the equatorial region of São João do Cariri, Brazil (7.4 ºS, 36.5 ºO) was used to identify and characterize variations associated with lunar tide. The solar time luminescence data of the three emissions; OH (6, 2), O155577 and 𝑂2(0−1) were smoothed with an average of three months to represent one month in order to reduce variability. The three emissions were subjected to spectral analysis using the Lomb-Scargle peridogram to identify the presence of tidal periodicities of each emission of airglow. The residual from each emission were obtained as a result of the subtraction of the reconstructed composite day using the components diurna, semidiurna and terdiuna of the solar tide, for each three months of measurements were used. This elimination of solar tide signals produced residual emissions of each data that are converted to lunar time and subjected to harmonic analysis to obtain the monthly amplitudes and phases of the lunar semidiurnal component for each of the three emissions. The time series obtained on a composite lunar day shows the lunar component. From the analysis of the data it was possible to identify the signature of the semidiurnal lunar tide in each emission throughout the year of 2004 in the equatorial region. / Medidas da luminescência atmosférica obtidas através de fotômetro multicanal na região equatorial em São João do Cariri, Brasil (7,4 ºS; 36,5ºO) são usadas para identificar e caracterizar variações associadas à maré lunar. Os dados de luminescência de tempo solar das três emissões; OH (6, 2), OI5577 e 𝑂2 (0- 1) foram suavizados com uma média de três meses para representar um mês, a fim de reduzir a variabilidade. As três emissões foram submetidas a análise espectral utilizando o peridograma de Lomb-Scargle para identificar a presença das periodicidades das marés em cada emissão de luminescência. Os resíduos de cada emissão foram obtidos como resultado da subtração do dia composto reconstruído utilizando as componentes diurna, semidiurna e terdiuna da maré solar. Para isto, foram utilizados três meses de medidas. Esta eliminação de sinais de maré solar produze emissões residuais de cada dado que são convertidas para o tempo lunar e submetidas a análises harmônicas para obter as amplitudes e fases mensais da componente semidiurna lunar para cada uma das três emissões. As séries temporais obtidas em um dia lunar composto mostra o componente lunar. A partir da análise dos dados foi possível identificar a assinatura da maré lunar semidiurna em cada emissão ao longo do ano de 2004 na região equatorial.