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Studies of internal gravity waves in the earth's upper atmosphere are of considerable interest. These waves play a very important role in the dynamics of the mesosphere and lower thermosphere (ML T) region where they can transfer large amounts of energy and momentum from the lower atmosphere via wave saturation and dissipation. In particular, small-scale short-period (50ms"1) . Another unusual characteristic of "frontal events" is an apparent reversal in contrast of the wave structures as imaged in the hydroxyl (OH) emission (peak altitude- 87 km) when compared with the oxygen (OJ) "green line" (557.7 nm) emission (peak altitude -96 km) that can sometimes occur. In one isolated case, observed from Haleakala, Hawaii, the bright wave crests in the OH emission appeared to propagated through a dark structureless sky, whereas in the OI emission the same waves appeared to propagate into a bright sky, leaving an apparently depleted emission in its wake. Recent theoretical studies based on noble measurements have shown that frontal events may be due to a "bore-like" intrusion that raises the OJ (557. 7 nm) layer by a few km and at the same time depresses the OH layer by a similar amount. However, studies of fronts and bores in the ML T region are exceptionally rare. I have discovered and analyzed 16 frontal events from image data recorded at Bear Lake Observatory, Utah ( 41.6°N, 111.6°W), over the past four years. I have investigated some of their properties such as their horizontal wavelengths, horizontal phase speeds, observed periods, and their directions of motion. In addition, I have made comparative measurements of their relative intensities in the OH and OI emissions. These studies provide the first "extensive" data set on such events detailing their morphology and dynamics and should provide important information necessary for a deeper understanding of their occurrence frequency and properties.

Aurora occurs in various shapes, one of which is the hitherto unreported phenomenon of auroral fragments. For three periods of occurrence of these fragments their properties were studied in detail during this master’s thesis, using mainly ground-based instrumentation located near Longyearbyen on Svalbard, Norway. A base dataset was constructed from 103 all-sky camera images, manually marking 305 fragments for further analysis. This thesis reports and describes the fragment observations during the observed events, including the auroral and geomagnetic context. Fragments generally seem to fall into two categories, the first being singular, apparently randomly distributed fragments, and the second being periodic fragments that occur in groups with a regular spacing close to auroral arcs. A typical fragment has a small horizontal size below 20 km, a short lifetime of less than a minute and shows no field-aligned extent in the emission. The fragments appear mainly west of zenith (73%) during the three observation nights, whereas their north-south distribution is symmetric around the zenith. Almost all of them exhibit westward drift, the estimated speed for one of the fragments passing the field of view of ASK is ∼1 km/s. A spectral signature can be seen in the green auroral wavelength of O at 557.7 nm and red emission line of N2 at 673.0 nm, but no emission enhancement was observed in the blue wavelengths. One fragment passing the EISCAT Svalbard radar’s field of view shows a local ion temperature increase in a small altitude range of ∼15 km, whereas there is no visible increase in electron density. This could be explained by fragment generation due to locally strong horizontal electric fields. A potential mechanism for this might be electric fields of atmospheric waves superposing with the converging electric fields of auroral arcs created by particle precipitation and the corresponding field-aligned currents. The resulting field would be perpendicular to the magnetic field and the auroral arcs, leading to wave-like density variations of excited plasma close to the arcs. Further study is required to verify this hypothesis and improve the understanding of fragment properties determined from the limited dataset used for this thesis.

Submitted by Alberto Silva Betzler (a_betzler@yahoo.com) on 2017-06-26T17:30:43Z No. of bitstreams: 1 tese_betzler.pdf: 7923258 bytes, checksum: 4fe67694cac7f7b562eafc89f55cce3b (MD5) / Approved for entry into archive by Flávia Sousa (flaviabs@ufba.br) on 2017-06-28T14:32:11Z (GMT) No. of bitstreams: 1 tese_betzler.pdf: 7923258 bytes, checksum: 4fe67694cac7f7b562eafc89f55cce3b (MD5) / Made available in DSpace on 2017-06-28T14:32:11Z (GMT). No. of bitstreams: 1 tese_betzler.pdf: 7923258 bytes, checksum: 4fe67694cac7f7b562eafc89f55cce3b (MD5) / Pequenos corpos do sistema solar são asteroides, cometas e poeira interplanetária. Os meteoros são produzidos pela interação de velozes grãos de poeira com a atmosfera terrestre. Esses fragmentos de rocha são presumivelmente oriundos dos asteroides e cometas, em passagens próximas da Terra, ou são transportados de outras regiões do sistema solar por processos dinâmicos. Como estes processos não são plenamente conhecidos, é importante a obtenção da maior quantidade possível de parâmetros físicos e orbitais dos meteoros. Dentro desse contexto, será apresentado o esquema de construção e operação de uma estação para detecção de meteoros, equipada com uma câmera ``all sky'' de TV. Este instrumento ajudou a suprir a carência de iniciativas de observação de meteoros no hemisfério sul. As magnitudes dos meteoros detectados pela estação foram bem modeladas por uma q-exponencial, que é uma função oriunda da mecânica estatística não extensiva de Tsallis. Além de sua validade no estudo dos meteoros, as q-distribuições são adequadas para modelar dados populacionais de asteroides, meteoritos e dos lampejos de luz (flashes) gerados pela colisão de meteoroides com massa da ordem de alguns quilogramas com a Lua. Os resultados obtidos das q-distribuições no estudo dos pequenos corpos do sistema solar são discutidos neste trabalho.

Schwerewellen transportieren Energie und Impuls aus den unteren in die oberen Atmosphärenschichten. Impulsflüsse und ihre Divergenz beschreiben dabei die Kopplung der Wellen mit der mittleren Zirkulation. Mit einer Methode von Hocking (2005) können Varianzen und Schwerewellenimpulsflüsse in der Mesosphäre / unteren Thermosphäre mit einem All-Sky Interferometric (SKiYMET) Meteorradar bestimmt werden. Diese Methode wurde auf die Datensätze des Meteorradars in Collm (51.3°N,13.0°E) angewandt. Erste Ergebnisse für die Varianzen und Impulsflüsse sowie speziell für die Höhenprofile des vertikalen Flusses zonalen Impulses im Jahresgang und die Untersuchung dessen auf periodische Schwankungen werden hier vorgestellt. / Gravity waves transport energy and momentum from the lower to the upper atmosphere. Momentum fluxes and their divergence describe the coupling of the waves with the background circulation. By using a method presented by Hocking (2005), wind variances and gravity wave momentum fluxes in the mesosphere/lower thermosphere can be determined with an all-sky interferometric (SKiYMET) meteor radar. This method has been applied to the data sets of the meteor radar at Collm (51.3°N,13.0°E). First results for the variances and momentum fluxes as well as for the height profiles of the vertical flux of zonal momentum, its seasonal cycle and periodic variations are presented.

Counting stars as a means of studying the structure of the Milky Way has a long history, which has progressed significantly with the undertaking of large-area surveys. Photographic surveys have been supplanted with the advent of CCD technology by digital surveys, which provide improved data quality allowing better calibration and fainter limits to be probed reliably. The INT/WFC Photometric H Survey of the Northern Galactic Plane (IPHAS) provides broad-band r0 and i0 photometry down to 20th magnitude at Galactic latitudes jbj < 5 . In this work I make use of the opportunity that IPHAS photometry provides to create stellar number density maps of the Northern Galactic Plane. I produce preliminary maps which are used to identify and exclude poor quality data during the preparation of the second data release of the survey (DR2). By crossmatching IPHAS against the AAVSO Photometric All-Sky Survey (APASS), I derive transformations between the two photometric systems, and measure the per-IPHAS- field magnitude shifts needed to bring the two surveys in line before a global calibration can be applied. Repeating the crossmatching approach between IPHAS and the Sloan Digital Sky Survey (SDSS), I derive transformations between the two surveys and assess their agreement before and after global photometric calibration, in order to gauge the improvement achieved. The effects of incompleteness begin to affect the fainter end of any photometric survey as a consequence of confusion and sensitivity limits. I present the application of artificial source insertion on every broad-band IPHAS DR2 image in order to measure the impact of incompleteness across the entire survey. These measurements are used to construct incompleteness-corrected density maps down to magnitude limits of r0 . 19 and i0 . 18 at an angular resolution of 1 arcminute. These maps represent a unique data product which has applications in studies of Galactic structure and extinction. I perform a cluster search on the i0-band density map, which in addition to returning 71 known clusters, identifies 29 overdensities unassociated with any known clusters. I compare the stellar densities given by my maps to those in simulated versions of the Milky Way generated by models of Galactic population synthesis. I examine the Gaia Universe Model Snapshot (GUMS), a catalogue which predicts the sky as may be observed by the Gaia mission. In order to make meaningful comparisons between GUMS and IPHAS I determine transformations between the two photometric surveys. The results of the comparison are mixed. I also make use of the 2003 Besan con model of Galactic population synthesis to generate catalogues of synthetic photometry along three sightlines in the IPHAS footprint in order to test different 3D extinction prescriptions. The lowest Galactic longitudes (` 30 ) prove to be particularly challenging to emulate, suggesting 3D mapping of optical extinction in the Galactic Plane is not yet a mature art. The main problem appears to be one of underprediction of the obscuration.

This thesis investigates the use of the Swedish Allsky Meteor Network (SAMN) for observing, identifying, and determining the orbits of satellites. The overall goal of this project is to determine the feasibility of using such a network for Space Situational Awareness (SSA) purposes, which requires identification and monitoring of objects in orbit. This thesis is a collaboration with the Swedish Defense Research Agency (FOI) to support their efforts in SSA. Within the frame of this project, the author developed software that can take data of observations of an object collected from the all-sky cameras of SAMN and do an Initial Orbit Determination (IOD) of the object. An algorithm that improves the results of the IOD was developed and integrated into the software. The software can also identify the object if it is in a database that the program has access to or, if it could not be identified, make an approximate prediction of when and where the object will be visible again the next time it flies over. A program that analyses the stability of the results of the IOD was also developed. This measures the spread in results of the IOD when a small amount of artificial noise is added to one or more of the observed coordinates in the sky. It was found that using multiple cameras at different locations greatly improves the stability of the solutions. Gauss' method was used for doing the IODs. The advantages and disadvantages of using this method are discussed, and ultimately other methods, such as the Gooding method or Double R iteration, are recommended for future works. This is mostly because Gauss' method has a singularity when all three lines of sight from observer to object lie in the same plane, which makes the results unreliable. The software was tested on a number of observations, both synthetic and real, and the results were compared against known data from public databases. It was found that these techniques can, with some changes, be used for doing IOD and satellite identification, but that doing very accurate position determination required for full orbit determination is not feasible. / Detta examensarbete undersöker möjligheterna att använda ett svenskt nätverk av allskykameror kallat SAMN (Swedish Allsky Meteor Network) för att observera, identifiera och banbestämma satelliter. Det övergripande målet med detta projekt är att bestämma hur användbart ett sådant nätverk skulle vara för att skapa en rymdlägesbild, vilken i sin tur kräver bevakning och identifikation av objekt som ligger i omloppsbana. Detta examensarbete är ett samarbete mellan Uppsala Universitet och FOI (Totalförsvarets Forskningsinstitut). Inom ramen för detta projekt har författaren utvecklat mjukvara som kan ta data från observationer av objekt utförda av SAMN och göra initiala banbestämningar av objekten. En algoritm som förbättrar resultaten av den initiala banbestämningen utvecklades och integrerades i programmen. Programmen kan också identifiera satelliter om de finns med i en databas som programmet har tillgång till eller förutsäga objektets nästa passage över observatören om det inte kunde identifieras. Ett annat program som analyserar känsligheten av resultaten av den initiala banbestämningen utvecklades också. Detta program mäter spridningen i resultat som orsakas av små störningar i de observerade koordinaterna på himlen. Det framkom att stabiliteten av resultaten kan förbättras avsevärt genom att använda flera observatörer på olika orter. I detta projekt användes Gauss metod för att göra banbestämningarna. Metodens för- och nackdelar diskuteras och i slutänden rekommenderas istället andra metoder, som Goodings metod eller Dubbel R-iteration, för framtida arbeten. Detta beror mest på att Gauss metod innehåller en singularitet när alla siktlinjer från observatören till objektet ligger i samma plan som varandra vilket gör resultaten opålitliga i de fallen. Programmen testkördes på ett antal olika observationer, både artificiella och verkliga, och resultaten jämfördes med kända positioner. Slutsatsen av arbetet är att de undersökta teknikerna kan, med vissa modifikationer, användas för att göra initiala banbestämningar och satellitidentifikationer, men att göra de väldigt precisa positionsbestämningarna som krävs för fullständig banbestämning är inte genomförbart.

No description available.

This MSc report discusses the attributes of W Ursae Majoris (W UMa) stars and an investigation into the Minimum Entropy (ME) method, a digital technique applied to the determination of their periods of variability. A Python code programme was written to apply the ME method to photometric data collected on W UMa stars by the All Sky Automated Survey (ASAS). Starting with the orbital period of the binaries estimated by ASAS, this programme systematically searches around this period for the period which corresponds to the lowest value of entropy. Low entropy here means low scatter (or spread) of data across the phase-magnitude plane. The ME method divides the light curve plot area into a number of elements of the investigators choosing. When a particular orbital period is applied to this photometric data, the resulting distribution of this data in the light curve plane corresponds to a speci c number of data points in each element into which this plane has been divided. This data spread is measured and calculated in terms of entropy and the lowest value of entropy corresponds to the lowest spread of data across the light curve plane. This should correspond to the best light curve shape available from the data and therefore the most accurate orbital period available. Subsequent to the testing of this Python code on perfect sine waves, it was applied, and its results compared, to the 62 ASAS eclipsing binary stars which were investigated by Deb and Singh (2011). The method was then applied to selected stars from the ASAS data base. / School of Environmental Sciences / M. Sc. (Astronomy)

This MSc report discusses the attributes of W Ursae Majoris (W UMa) stars and an investigation into the Minimum Entropy (ME) method, a digital technique applied to the determination of their periods of variability. A Python code programme was written to apply the ME method to photometric data collected on W UMa stars by the All Sky Automated Survey (ASAS). Starting with the orbital period of the binaries estimated by ASAS, this programme systematically searches around this period for the period which corresponds to the lowest value of entropy. Low entropy here means low scatter (or spread) of data across the phase-magnitude plane. The ME method divides the light curve plot area into a number of elements of the investigators choosing. When a particular orbital period is applied to this photometric data, the resulting distribution of this data in the light curve plane corresponds to a speci c number of data points in each element into which this plane has been divided. This data spread is measured and calculated in terms of entropy and the lowest value of entropy corresponds to the lowest spread of data across the light curve plane. This should correspond to the best light curve shape available from the data and therefore the most accurate orbital period available. Subsequent to the testing of this Python code on perfect sine waves, it was applied, and its results compared, to the 62 ASAS eclipsing binary stars which were investigated by Deb and Singh (2011). The method was then applied to selected stars from the ASAS data base. / Environmental Sciences / M. Sc. (Astronomy)