Meteors enter earth's atmosphere with a great amount of kinetic energy. As a result of this atmospheric contact, many meteors will be burned up before they can make it to earth's surface, but not before they cause atmospheric disturbances. The SuperDARN HF radar is designed to measure the ionosphere, typically to create hemisphere wide maps of ionospheric plasma convection, but meteor events are attributed to noise experienced in its data. This thesis first brings together plasma physics understanding with currently available research to clarify the physical behaviors that must be considered to evaluate radar data. The implications of this towards SuperDARN findings is examined in two parts. First, how a meteor's atmospheric interaction is recorded by the SuperDARN HF radar is evaluated. To do this, the physical interaction the meteor has with the atmosphere is examined from the sub-atomic to atmospheric scale. Previous research that used other radars to find these interactions is analyzed to create an understanding of a possible SuperDARN HF radar outcome and provide a new comparison of radars. This understanding is compared against meteor event and location based SuperDARN data to select an optimal event. The second part of the SuperDARN analysis reviews meteor event options based on the time and location of a meteor event meeting defined parameters. Common SuperDARN analysis tools are applied. The data saved by SuperDARN is examined for unique results. Finally, the practicality and meaning of results is considered. / Master of Science / SuperDARN radars emits radio waves that reflect within earth's ionosphere to study how it changes. The ionosphere is a part of earth's upper atmosphere; many of the atoms there are hydrogen and helium. Lower in earth's atmosphere, the sun's energy is just felt as heat that gets dissipated at night or when clouds move in front of the sun. In the thin upper atmosphere, this energy does not transfer as easily, so the atoms ionize to store energy as charge. This can occur lower down in earth's atmosphere, such as when a hypersonic traveling meteor impacts the air with a lot of energy. This ionized trail of atoms behind a meteor is called a meteor trail. Just as the ionosphere can reflect some radio waves, meteor trails can reflect radio waves. It was questionable how well these reflections could be found in SuperDARN data since that radar looks over a large area and meteor trails are comparatively small. This research seeks to answer that. Current research on meteor trails and analysis with radar was analyzed along with a review of the underlying physics concepts involved. Once this background is established, actual SuperDARN radar data is analyzed for a time and place that gives the best chance of seeing some change as a result of a meteor trail.

In this report, a number of different Javascript-frameworks have been compared. The study is conducted at CSN (Centrala studiestödsnämnden). The study consists of two main parts, an evalua- tion through the literature study and an evaluation of the implementa- tion. The first part of the survey has Javascript-frameworks Angular2, Aurelia, Ember, Meteor and React comparisons. Together with CSN, a few criteria have been developed which will then be awarded points between one and five depending on how well a Javascript-framework meets a specific criterion. Five points are given when the Javascript- framework meets the entire criterion, one point is given when it partial- ly meets the criterion. After the first part of the investigation, Angular2 and Aurelia found that they would move on to the implementation phase. The implementation consists of a couple of windows from the existing service "Mina tjänster". In the evaluate implementation measures time for implementation, web browsing time, and number of code rows. From this it was found that Aurelia has less number of code rows than Angular 2. The reading time for Angular 2 is three times longer than Aurelia. In the evaluation of how difficult it is to implement the two frameworks, Angular 2 is considered to be "Average" and Aurelia to "Hard". The Javascript-framework recommended for CSN is Angular 2. This is because much more documentation about Angular 2 is available, and the difficulty is lower for Angular 2. The startup of a project is also much easier in Angular 2, which means that it requires less time to get into the framework. / Sammanfattning: I denna rapport har ett par olika Javascript-ramverk jämförts. Studien är utförd på CSN (Centrala studiestödsnämnden). Undersökningen består av två huvuddelar, en utvärdering genom litteraturstudie samt en utvärdering av implementation. I första delen av undersökningen har Javascript-ramverken Angular2, Aurelia, Ember, Meteor och React jämförts. Tillsammans med CSN har ett par kriterier tagits fram som det sedan kommer att delas ut poäng mellan ett till fem beroende på hur väl ett Javascript-ramverk uppfyller ett specifikt kriterium. Fem poäng ges ut då Javascript-ramverket uppfyller hela kriteriet, ett poäng ges ut då det delvis uppfyller kriteriet. Efter första delen av undersökningen kom det fram till att Angular2 och Aurelia skulle gå vidare till implemente- ringsfasen. Implementeringen består utav ett par fönster från den befintliga tjänsten ”Mina tjänster”. I utvärderingen av implementation mäts tid för implementering, inläsningstid för webbapplikationen samt antalet kodrader. Ur detta konstaterades det att Aurelia har mindre antalet kodrader än Angular 2. Inläsning tiden för Angular 2 är tre gånger längre än Aurelia. Men i bedömningen om hur svårt det är att implementera de bägge ramverken bedöms Angular 2 till nivån ”Me- del” och Aurelia till ”Svår”. Det Javascript-ramverk som rekommende- ras till CSN är Angular 2. Detta grundas på att det finns betydligt mycket mer dokumentation om Angular 2, samt att svårighetsgraden är lägre för Angular 2. Uppstarten av ett projekt är även mycket enklare i Angular 2, vilket betyder att det kräver mindre tid för att sätta sig in ramverket.

Seit August 2004 wird am geophysikalischen Observatorium Collm (51.3° N, 13° E) ein SKiYMET Meteor-Radar betrieben. Dieses liefert seitdem kontinuierliche Temperaturwerte und Windmessungen. Die Grundlage des Messverfahrens stellt ein stetiger Fluss von Meteoren dar, die in einer Höhe von 75-105 km verglühen. Aus den mit dem Radar bestimmten Positionen der Meteore können Temperaturen in der Mesopausenregion abgeschätzt werden. Für die Darstellung des Jahresganges wurden Tagesmittelwerte genutzt. Dabei tritt im Sommer ein Temperaturminimum mit ca. 170 K auf. Im Winter ist die Situation durch Temperaturen von 205 K und starker planetarer Wellenaktivität gekennzeichnet. Desweiteren konnte eine Klimatologie für die ganz-, halbtägigen und 8-stündigen Gezeiten erstellt werden. / Since August 2004 a SKiYMET meteor-Radar is operated at the geophysical Observatory Collm, Germany (51.3° N, 13° E). The radar provides a continuous time series of temperature and wind measurements. The bases for this method is a steady flux of meteors entering the earth’s atmosphere. In an altitude between 75-105 km they form a cylindrical plasma trail, which reflects radar signals. Hence the system can determine the positions of the meteors, which are used to estimate mesopause region temperatures. For the diagram of the seasonal change we used daily mean temperatures. The summer shows a temperature minimum with 170 K. During the Winter we observed temperatures about 205 K and a stronger planetary wave activity. Another part was the generation of a climatology for the diurnal, semidiurnal und terdiurnal tide.

This thesis presents observations of the dynamical features of the stratosphere, mesosphere and lower thermosphere. These are made from various observational techniques and model comparisons. A focus of the work is the two-day wave at high latitudes in the MLT region. This has revealed significant wave amplitudes in both summer and winter. However, these waves are shown to have very different origins. Using satellite data, the summertime wave is found to be the classic quasi-two-day wave which maximises at mid-latitudes in the MLT region. The wintertime wave is found to be a mesospheric manifestation of an eastward-propagating wave originating in the stratosphere and likely generated by barotropic and baroclinic instabilities in the polar night jet. The horizontal winds from Meteor and MF radars have been used to measure and produce climatologies of the Lunar M2 tide at Esrange in the Arctic (68°N), Rothera and Davis in the Antarctic (68°S), Castle Eaton at mid-latitude (52°N) and Ascension Island at Equatorial latitudes (8°S). These observations present the longest period of lunar semi-diurnal tidal observations in the MLT region to date, with a 16-year dataset from the UK meteor radar. Comparisons with the Vial and Forbes (1994) lunar tidal model are also made which reveal generally good agreement. Non-migrating lunar tides have been investigated. This uses lunar tidal results from equatorial stations, including the Ascension Island (8°S) meteor radar. Also lunar tidal results from the Rothera meteor wind radar (68°S, 68°W) and the Davis MF radar (68°S, 78°E) are considered. Both of these stations are on the edge of the Antarctic continent. It is demonstrated that there are often consistent tidal phase offsets between similar latitude stations. This suggests that non-migrating modes are likely to be present in the lunar semi-diurnal tidal structure and have significant amplitudes.

Gravity waves play a fundamental role in driving the large-scale circulation of the atmosphere. They are influenced both by the variation in their sources and the filtering effects of the winds they encounter as they ascend through the atmosphere. In this thesis we present new evidence that gravity waves play a key role in coupling the troposphere, stratosphere and mesosphere. In particular, we examine the connection of gravity waves to two important large-scale oscillations that occur in the atmosphere, namely the Madden-Julian Oscillation (MJO) in the troposphere and the Mesospheric Semi-Annual Oscillation (MSAO). We present the first ever demonstration that the MJO acts to modulate the global field of gravity waves ascending into the tropical stratosphere. We discover a significant correlation with the MJO zonal-wind anomalies and so suggest that the MJO modulates the stratospheric gravity-wave field through a critical-level wave-filtering mechanism. Strong evidence for this mechanism is provided by consideration of the winds encountered by ascending waves. The Ascension Island meteor radar is used for the first time to measure momentum fluxes over the Island. These measurements are then used to investigate the role of gravity-wave in driving a dramatic and anomalous wind event that was observed to occur during the first westward phase of the MSAO in 2002. Gravity waves are shown to play an important role in driving this event, but the observations presented here also suggest that the current theory of the mechanism describing these anomalous mesospheric wind events is not valid. Both of these studies highlight the critical importance of gravity waves to the dynamics of the atmosphere and highlight the need for further work to truly understand these waves, their processes and their variability.

No description available.

Les météoroïdes, les astéroïdes et les comètes ont été en interaction permanente avec la Terre pendant son existence. Lorsqu'un objet, tel qu'une comète ou un astéroïde, tourne autour du Soleil, il peut laisser des fragments de matière derrière lui. Il y a une relation implicite entre les fragments et leurs corps parents. Le champ gravitationnel de la Terre capte les fragments et quelques fois le matériel extraterrestre est retrouvé au sol sous la forme des météorites. L'étude de ces objets et le lien entre eux peuvent aider à comprendre les conditions de formation et d'évolution du Système solaire, les conditions de développement de la vie sur Terre, les processus chaotiques dans le Système solaire, la sécurité de la Terre et peut-être, l'industrie spatiale.Tous les objets dans le Système solaire sont caractérisés par leurs orbites et les flux de météoroïdes ont des orbites similaires avec les objets qui les produisent. Pour cette raison, la méthode la plus courante d'identification du corps parental est basée sur les similarités des orbites, également appelées critères de discrimination ou critères-D. Dans mon travail, j'ai utilisé trois critères D-Criteria pour l'association des corps parents. Je définis un seuil pour chaque mesure en utilisant une nouvelle méthode de sélection de seuil. En outre, j'ai étudié les objets associés stabilité orbitale, dans le sens du temps de Lyapunov et leurs propriétés physiques. En raison des similitudes entre les flux de météorites et leurs corps parents, il est nécessaire que les associations appartiennent à la population d'astéroïdes géocroiseurs. L'observation de cette population d'objets est cependant difficile. La géométrie favorable pour les observations d'un géocroiseur est limité a trois ou cinq fois par siècle. Pour cette raison j'ai créé un programme d'observation, qui vise à obtenir des données physiques pour les objets associés qui n'ont pas de données physiques. Lors de mes recherches, j'ai pu associer 296 géocroiseurs à 28 pluies de météores; parmi eux, 73 astéroïdes satisfaisants les trois critères utilisés. Du point de vue dynamique, mon échantillon contient 82 % d'astéroïdes de type Apollo et 7 % sont classés comme potentiellement dangereux, 15,3 % sont sur des orbites cométaires et 84,3 % sur des orbites d'astéroïdes. Du point de vue des données physiques, j'ai trouvé deux astéroïdes qui sont des rotateurs rapides, donc ils ne peuvent pas générer de météores. D'un autre côté, j'ai également trouvé un astéroïde binaire associé et un astéroïde tumbling, des objets avec une forte probabilité d'être des corps parents. J'ai également réussi à trouver des similitudes entre 5 météorites et 5 astéroïdes associés avec des données physiques et j'ai obtenu des données d'observation pour trois astéroïdes associés. / Meteoroids, asteroids, and comets have been permanently interacting with Earthduring its existence. When an object, such as a comet or an asteroid, revolve around the Sun it may leave fragments of matter behind it and if this object is in Earth’s proximity, those fragments are gathered by the planet gravity. The study of these objects and the link between them can help in the understanding of the formation and evolution conditions of the Solar System, the conditions of developing the life on Earth, the chaotic processes in the Solar System, Earth security and maybe, in future, space industry.All objects within the Solar System are characterized by their orbits andthe meteoroid streams have similar orbits with the objects that produce them. For that reason the most common method of parent body identification is based onorbits similarities, also known as discrimination criteria or D-Criteria. In my work I used three D-Criteria metrics for parent body association. I set a threshold for each metric by using a new threshold selection method. Moreover, I investigated the associated objects orbital stability, in the Lyapunov time sense and their physical properties.Due to the similarities between meteoroid streams and their parent bodies,it is required for the associations to belong to Near Earth Asteroids population. But for this population is difficult to obtain data. The favorable geometry for these objects observations occurs five times per century. For this reason was created an observational program, that aims to obtain physical data for the associated objects that do not have physical data.My results consist from 296 asteroids that were associated with 28 meteorshowers, from which 73 asteroids satisfied all the criteria used. From the dynamical perspective, my sample contains 82% of Apollo asteroids and 7% are classified as potential hazardous, 15.3% are on cometary orbits and 84.3% are on asteroidal orbits. From the physical data perspective, I found two asteroids that are fast-rotators, therefore they can not generate meteors. On the other hand, I also found associated one binary asteroid and one tumbling asteroid, objects with a high probability of being parent bodies.I also managed to find similarities between 5 meteorites and 5 associatedasteroids with physical data and I obtained observational data for three associated asteroids.

<p>This thesis concerns the fate of the meteoric smoke in the Middle Atmosphere, and its effect on ice phenomena such as noctilucent clouds (NLC) and polar stratospheric clouds (PSC). </p><p>The potential role of NLC as tracer for mesospheric processes and variability, and as a tool for monitoring this remote and inaccessible region, has generated substantial interest within the scientific community. The nucleation of ice in such a dry environment is not trivial. Supersaturation is considered too low for homogeneous nucleation. Hence, pre-existing condensation nuclei are deemed necessary, with smoke particles having long been considered the most likely candidate. Here we show that the atmospheric circulation transports meteoric smoke particles away from the polar region before they coagulate large enough to efficiently act as ice condensation nuclei. We also show that the charging of meteoric smoke, in combination with deviations from the mean thermal state, may solve this dilemma by significantly altering the ice nucleation properties of smoke. Thus, while it is highly questionable whether neutral smoke can provide sufficient amounts of condensation nuclei for ice formation at the polar summer mesopause, charged meteoric smoke proves to be a promising candidate to explain mesospheric ice phenomena as we observe them.</p><p> We further show that the bulk of the meteoric material is transported to the Arctic winter stratosphere, yielding significantly higher concentrations of meteoric smoke in the region of PSC nucleation than has previously been believed. Our new predictions of meteoric smoke in this region may thus shed new light on open questions relating to PSC nucleation.</p>

This thesis concerns the fate of the meteoric smoke in the Middle Atmosphere, and its effect on ice phenomena such as noctilucent clouds (NLC) and polar stratospheric clouds (PSC). The potential role of NLC as tracer for mesospheric processes and variability, and as a tool for monitoring this remote and inaccessible region, has generated substantial interest within the scientific community. The nucleation of ice in such a dry environment is not trivial. Supersaturation is considered too low for homogeneous nucleation. Hence, pre-existing condensation nuclei are deemed necessary, with smoke particles having long been considered the most likely candidate. Here we show that the atmospheric circulation transports meteoric smoke particles away from the polar region before they coagulate large enough to efficiently act as ice condensation nuclei. We also show that the charging of meteoric smoke, in combination with deviations from the mean thermal state, may solve this dilemma by significantly altering the ice nucleation properties of smoke. Thus, while it is highly questionable whether neutral smoke can provide sufficient amounts of condensation nuclei for ice formation at the polar summer mesopause, charged meteoric smoke proves to be a promising candidate to explain mesospheric ice phenomena as we observe them. We further show that the bulk of the meteoric material is transported to the Arctic winter stratosphere, yielding significantly higher concentrations of meteoric smoke in the region of PSC nucleation than has previously been believed. Our new predictions of meteoric smoke in this region may thus shed new light on open questions relating to PSC nucleation.

Modem technology has revived interest in the once popular area of meteor scatter communications. Meteor scatter systems offer reliable communications in the 500 to 2000 km range all day, every day. Recent advances in microprocessor technology have made meteor scatter communications a viable and cost effective method of providing modest data rate communications. A return to the basic fundamentals has revealed characteristics of meteor scatter propagation that can be used to optimize the protocols for a meteor scatter link. The duration of an underdense trail is bounded when its initial amplitude is known. The upper bound of the duration is determined by maximizing the classical underdense model. The lower bound is determined by considering the volume of sky utilized. The duration distribution between these bounds is computed and compared to measured values. The duration distribution is then used to specify a fixed data rate, frame adaptive protocol which more efficaciously utilizes underdense trails, in the half duplex environment, than a non-adaptive protocol. The performance of these protocols is verified by modeling. / Thesis (Ph.D.)-University of Natal, Durban, 1987.