Dissertations / Theses on the topic 'Terrestial Magnetism'

Signaling and sensing with rotating magnet sources have both Terrestrial and Extraterrestrial applications. The dual spinning magnet unit presented in this paper is a simple, lightweight solution to help understand soil densities and locate water and ice pockets, for example, on Mars. Traditional magnetic telemetry systems that use energy-inefficient large induction coils and antennas as sources and receivers are not practical for extraterrestrial and remote field sensing applications. The recent proliferation of strong rare-earth permanent magnets and high-sensitivity magnetometers enables alternative magnetic telemetry system concepts with significantly more compact formats and lower energy consumption. There are also terrestrial applications, for example, subterranean objects such as underground infrastructure and unexploded ordnances (UXO) that are often unmapped and difficult to find on Earth. Current ground penetrating radar units are expensive, large, and heavy. The research presented explores the viability and possibility to develop a unit that will induce an oscillating magnetic field with controllable shape to reliably locate buried ferromagnetic and non-ferromagnetic objects while remaining lightweight and cost effective. A Dual Rotating Magnet (DRM) design is presented. Experiments and numerical simulations assess the system for terrestrial and extraterrestrial detection of: 1) differences in soil densities, 2) water and ice pockets at shallow depths in the subsurface, and 3) subterranean ferromagnetic and non-ferromagnetic objects of interest.

This thesis explores British-led efforts to observe and map the earth’s magnetic field between 1833 and 1857. In doing so, the thesis examines how magnetic instruments, magnetic observers and magnetic instructions were mobilised in and across multiple geographies, from the Canadian Arctic, to the island of St Helena, to Van Diemen’s Land in the southern hemisphere and at many sites in between. Interest in terrestrial magnetic research burgeoned and was crystallised during the early nineteenth century in Britain and abroad and resulted in the creation of systems of physical observatories and the organisation of magnetic surveys. This work addresses what it meant to coordinate such a network by scrutinising what is popularly known as “the magnetic crusade”, but which was more commonly referred to at the time as the British magnetic scheme. There were several individuals involved in the formation of this scheme but this thesis focuses on two in particular: Edward Sabine and Humphrey Lloyd. In the correspondence of these two figures, we can follow the process by which terrestrial magnetic research was disciplined, its participants educated, its observational data organised and its instruments developed, deployed and used at different stations across the globe. This work seeks to extend and at times complicate our understanding of what it meant to coordinate a big Victorian scientific pursuit and explores among other things the management of instruments in different geographic contexts; the experience of scientific servicemen in the observatory and during surveying efforts; the space in which magnetic data were handled and the processes employed in reducing these data. In all, this thesis aims to recover the several different practices of place that attended the organisation of what was considered in the first half of the nineteenth century to be the greatest scientific endeavour yet pursued.

In this thesis ground-based observations of the terrestrial magnetic field have been used to studythe characteristics of a special type of magnetospheric pulsation called Pi2. The magnetic fielddata used was observed by the SANAE pulsation magnetometer, located at Antarctica. Severalcharacteristics of the pulsations have been examined for 137 events. For all the events aninjection of energetic particles could be seen simultaneously in the magnetosphere, which is anindication of a substorm onset. The particle injection was confirmed by data from theLANL/SOPA electron flux satellites, located in geosynchronous orbits at 6.6 RE height. Themain frequency of the events was concentrated in the lower part of the defined Pi2 range (7-25mHz) with a mean of 11.3 mHz. The polarisation parameters and the rate of damping wereexamined for 20 clear events. The damping increment had typical values of 0.05-2.Thepolarisation azimuth was directed in the North-East/South-West direction for most of the eventsand the sense of polarisation showed a transition from counter clockwise before 0200 local timeto clockwise afterward.

This thesis investigates the topology of the magnetic field in the solar corona, due to a variety of source configurations and types. To fully understand the complex behaviour of the Sun's magnetic field, it is important to have a complete description of the features present in its structure. The magnetic topologies due to network source configurations are investigated using both the point source description and the continuous source description. A series of case studies involving an emerging bipole in a hexagonal arrangement to simulate a supergranular cell are studied. This has a particular focus on the behaviour of coronal nulls located in the topology, and a particular case may form the underpinning of a model for polar plumes. A new topological feature, called a null-like point, is defined by relaxing the definition of a magnetic null point. Separatix-like surfaces, originating from null-like points, allow quasi-separatrix layers to be found in magnetic topologies due to continuously distributed sources. The squashing factor, Q, is mapped across the source configuration, highlighting the locations of the quasi-separatrix layers. Finally, an algorithm is developed which automatically detects and classifies magnetic events local to X-ray bright points (XBPs). Significant peaks are identified in the gradients of flux curves (positive, negative and absolute flux) local to XBP footpoints, allowing instances of flux emergence and cancellation to be identified and linked to the onset and demise of the XBPs studied. The algorithm correctly classifies 90% of all emergence and cancellation events related to the studied XBPs.

The turn of the twentieth century was an era of intense exploratory and scientific activity on and around the Antarctic continent. A few campaigns specialised in either territorial discovery or scientific inquiry, but most combined exploration and science in a comfortable alliance that produced results in both arenas. In recent years the scientific achievements of the Discovery expedition (1901-04) have been the subject of renewed analysis, but it is never clear what criteria, if any, are being applied to support statements about scientific success. This research is founded on a case study focused on the magnetic science program of the Discovery expedition commencing with preparations, performance of magnetic observing at sea and ashore, post-expedition management of the products of research, and finally, arrangements for publication. The case study forms the basis for firstly, identifying the indicators of scientific success and secondly, an analysis of the relative contributions of the drivers promoting quality scientific outcomes during the era of Antarctic scientific exploration between 1898 and 1914. The principal elements contributing to superior outcomes are identified as the human elements of preparation, leadership, scientific practice, skill, knowledge development and finally post-expedition management of data or collections gathered during fieldwork. No single element guarantees scientific success; it is a product of a combination of factors, but failure in just one facet can undermine outcomes fatally. The effectiveness of the relationship between these factors determines the degree of success or failure of a program. Achieving the potential of a research program relies on elements coming together in a timely and synergistic manner in combination with a measure of luck. There was confusion between the magnetic work intended to provide improved charts for navigation purposes and the scientific research designed to help solve the causes of terrestrial magnetism and it’s effects. The magnetic work of the expedition was divided into three distinct operations. Firstly, observations were made at sea in the ship’s purpose built magnetic observatory and using a recently developed instrument for the determination of magnetic dip and force. The results were ultimately never published due to the inadequacy of the instrument and the difficulties of taking reliable observations at sea. Secondly, a fixed observatory was established at the base station in Antarctica where a different set of instruments recorded the magnetic elements almost continuously over the two-year stay of the expedition. There was sufficient data from those observations to form the core of the scientific reports on terrestrial magnetism, but large amounts of data were considered unreliable and either discarded, or included with cautionary notes. Thirdly, magnetic observations made on exploratory sledging journeys away from the ice station added evidence for theoretical determination of the location of the South Magnetic Pole and for mapping the lines of equal magnetic declination radiating from it. The conclusions from these journeys were brought into doubt by evidence from later expeditions. During fund raising and promotion of the expedition, Sir Clements Markham, President of the Royal Geographical Society stated firstly, that products of the magnetic research would include new magnetic charts of value to mariners and secondly, there would be significant leaps in knowledge informing magnetic theory. These were ambitious objectives and neither were realised, although the data collected did add to knowledge of the characteristic fluctuations of the magnetic field at high latitudes. Collaborative arrangements planned between the Discovery, the German Gauss expedition and various established land observatories never reached their potential. This was partly due to an error in the timing of synchronous observations, but mainly a result of collapse of the intended post-expedition data sharing arrangements related to rejection by the Germans of the unreliable data from Discovery and failure by the English to publish data in a mutually useful format. The thesis closes with analysis of how well the Discovery’s outcomes matched their potential and concludes that, with respect to magnetic science, institutional failures led to avoidable deficiencies in areas of recruitment, training, governance and leadership, procedures, instrumentation and post-expedition management of data and publication preparations.

Terrestrial auroras are visible-light events caused by charged particles trapped by the Earth's magnetic eld precipitating into the atmosphere along magnetic eld lines near the poles. Auroral events are very dynamic, changing rapidly in time and across large spatial scales. Better knowledge of the low of energy during an aurora will improve understanding of the heating processes in the atmosphere during geomagnetic and solar storms. The Auroral Spatial Structures Probe is a sounding rocket campaign to observe the middle-atmosphere plasma and electromagnetic environment during an auroral event with multipoint simultaneous measurements for fine temporal and spatial resolution. The auroral event in question occurred on January 28, 2015, with liftoff the rocket at 10:41:01 UTC. The goal of this thesis is to produce clear observations of the magnetic eld that may be used to model the current systems of the auroral event. To achieve this, the attitude of ASSP's 7 independent payloads must be estimated, and a new attitude determination method is attempted. The new solution uses nonlinear least-squares parameter estimation with a rigid-body dynamics simulation to determine attitude with an estimated accuracy of a few degrees. Observed magnetic eld perturbations found using the new attitude solution are presented, where structures of the perturbations are consistent with previous observations and electromagnetic theory.

Electromagnetic fields (EMF) produced by high voltage (HV), submarine transmission cables leading from offshore wind energy generation facilities could affect foraging or migratory behaviors of electro-receptive fishes, including endangered Atlantic Sturgeon. However, no published studies have quantitatively evaluated the possible behavioral effects of EMF exposure on sturgeon during residence in coastal waters. This study evaluated behavioral responses by sub-adult Atlantic Sturgeon to electromagnetic and magnetic fields under controlled laboratory conditions. Fabricated EMF generators were used to emulate a range of field EMF conditions that migratory fishes could encounter in proximity to submarine HV sources. Sensor arrays and digital video recorders synoptically quantified EMF conditions and fish behaviors during experimental trials. This thesis will describe the unique, experimental EMF generator/sensor array, present results of the behavior study, and suggest implications of the findings for Atlantic Sturgeon management and conservation. 45 trials were conducted over the course of the study. Study fish were subjected to 3 different field strengths (5µT, 100 µT, 1000 µT), generated using both AC and DC current. Time spent in generated field area, number of passes through the field area, and swimming speed were used to quantify behavioral changes in test subjects. From the data collected and analyzed there was no evidence indicating a change in fish behavior due to the influence of field strengths, field orientations, or field types used during the study.

Les méthodes d'induction électromagnétique permettent de caractériser la conductivité électrique des matériaux, dont les corps planétaires telluriques, depuis les couches superficielles de la croûte jusqu'aux zones les plus internes, dans le manteau inférieur. Pour une source de champ électromagnétique donnée, des courants sont induits dans les matériaux qui y sont soumis. Avec l'essor des données magnétiques satellitaires, de nouvelles méthodes d'analyse des données magnétiques permettent d'obtenir des images unidimensionnelles de la structure électrique de ces corps car la structure spatio-temporelle de la source électromagnétique en est bien connue. Les travaux de mon doctorat ont eu pour but de mettre en place une nouvelle méthode d'analyse permettant de déterminer des modèles de structure interne globaux pour n'importe quel corps du système solaire pour lequel on dispose de longues séries temporelles magnétiques satellitaires. Après avoir testé cette méthode sur des modèles synthétiques et l'avoir appliqué au cas de données réelles terrestre pour lesquelles des études d'induction électromagnétiques antérieurs permettent d'avoir un a priori sur le modèle de conductivité électrique attendu, nous avons obtenu les premiers modèles de conductivité électrique martien en utilisant les données magnétiques du satellite Mars Global Surveyor. Ces résultats nous ont permis de valider des modèles de structure interne antérieurs établis à partir d'analyses géochimiques et minéralogiques des météorites martiennes. Cette méthode innovante est aujourd'hui la seule capable d'obtenir une image électrique des manteaux telluriques à partir de données magnétiques satellitaires pour des corps autres que la Terre ou la Lune et pour lesquels aucun a priori sur la structure spatio-temporelle du champ électromagnétique inducteur externe n'est nécessaire
My Ph.D. work consists in the investigation of satellite magnetic data to infer the deep internal conductivity distribution. I developed a new global electromagnetic induction method applied to planetary magnetic datasets without strong a priori hypothesis on the external inducing source field. My method is based on a spectral correction of gapped data magnetic time series to restore the time spectral content of the source field. This external source depends on the planetary environment and is therefore different for each planetary bodies. The method aims at recovering with a maximum accuracy internal and external spherical harmonic coefficients of transients fields, whose ratio is used as a transfer function to retrieve the internal distribution of electrical conductivity. While for the Earth, a good proxy of the source field activity is the Dst index, no such proxy exists for other planets. Hence, for our study of Mars transient magnetic field from MGS, one of the major part of my work is the determination of an appropriate continuous proxy for the external variability. On Earth the external electromagnetic source is well known, and may be described by a spherical harmonic geometry dominated by the dipole term. This source field may be characterized using a magnetic activity index named the Dst index. The method has been tested on synthetic data generated within the framework of SWARM mission. This mission consists of a 3 satellites constellation. One of the main objectives is to infer the 3D electrical distribution in the deep Earth. SWARM synthetic data consist in a time series of spherical harmonic (SH) coefficients, external and internal, generated from a simple non-realistic 3D model. In this model, several regional and local conductors, in a radially symmetric 3 layers model have been embedded. Using this dataset, our method give satisfactory results. We have been able to obtain the external and internal SH coefficients - for the first SH degree, which is known to be the most energetic degree of the external source - using only one of the 3 synthetic time series. Then, the method has been used on real data from Ørsted. In this case, we had to pre-process the data to correct from ionospheric and aligned currents contributions. We developed a statistical analysis to remove the ionospheric field using 2 geomagnetic indices : AL and Kp. Hence, we have enlarged data toward higher and lower latitudinal zones than what has been done in previous works. Finally, we have been able to obtain 1D conductivity models, which fits reasonably with existing conductivity data in the deep Earth. Finally, we worked on Mars Global Surveyor (MGS) data. One of the most time consuming parts of this work was the determination of an appropriate continuous proxy for the external variability in the vicinity of Mars. Without any measurements of the IMF (Interplanetary Magnetic Field) during MGS sciences acquisition, we have used ACE (Advanced Composition Explorer) data. This satellite orbits around the L1 point of the Sun-Earth system, measuring solar wind magnetic characteristics. We have time-shifted ACE data to Mars position for 4 temporal windows where Mars and Earth were closed to the same Parker's spiral's arm, and finally determined a proxy explaining the major part of the variability observed in Mars data. Despite numerous gaps in MGS data, we have been able to establish the 1D conductivity distribution, fitting reasonably existing geochemical models. Although the method may be unstable for some cases, we obtained satisfactory results for in depth conductivity of the planet

碩士
國立臺北科技大學
電機工程系研究所
102
The aim of this research is to design Three-Dimensional Magnetic Sensor, and uses the readout circuit to amplify sensor’s output voltage. The purpose of this paper is uses Three-Dimensional Magnetic Sensor to sense terrestrial magnetism. While integrate all circuit in one chip, reducing the Sensor volume and production cost. In this paper we present Three-Dimensional Magnetic Sensor consist of one Z-axis magnetic sensor and one XY-axis magnetic sensor, then use readout circuit and low pass filter to amplify and filter, finally the instrument amplifier output the voltage result. The measure result Sensor output voltage range is from 1 mV to 5 mV, and magnetic field range is from 0 Guess to 40 Guess, sensitivity is 9 V⁄AT to 19 V⁄AT.

碩士
銘傳大學
資訊傳播工程學系碩士班
106
As the popularity of smart mobiles and users will be able to rely on smart mobiles with global satellite positioning systems (global positioning system, GPS) to get their current location in the field. However, GPS cannot obtain the indoor location information when the user is inside a building. Therefore, it needs to use other systems to get indoor positioning, like traditional wireless indoor positioning technology, such as Wi-Fi and Bluetooth technology. But these techs face difficulties such as human shields, multi-path, radio frequency interference to positioning accuracy with serious deviations. In recent years, some research uses the Geomagnetic do indoor positioning of the possibility of smart mobiles, because of mobiles have the magnetometer, and the magnetometer is not affected by people shield. This study also conducts experiments on some factors that affect the magnetic field sensing. And analyzes the conditions that affect the magnetometer's measuring. Finally, we use k-nearest nearest neighbor algorithm (k-nearest nearest neighbor, KNN) and magnetic field weighting for positioning, the positioning accuracy can be achieved 91.7% and the average of error distance is 0.76 meter.

Mars was assumed to be very similar to Earth in terms of topography, water, magnetic field, and even the existence of life. However, exploration of the planet in the 1960s by the Mariner missions showed us a very different planet, one very unlike our own. The later discovery by the Mars Global Surveyor (MGS) of the lack of a globally generated magnetic field proved just how different Mars is from Earth. The discovery of strong magnetic remanence (on the order of 20 – 30 A/m) on Mars implies that at some point in Mars’ history there was a magnetic field, and therefore a dynamo. Since a globally active magnetic field is not present, it can also be assumed that the dynamo ceased generation. Basaltic rocks on Earth typically have magnetic remanences between 1 to 4 A/m and do not usually hold on to those remanences for billions of years. In this study, I utilized the information available on the geochemistry, age, and magnetics of Martian rocks in an attempt to find appropriate terrestrial analogs. Seven Earth locations of basaltic rocks (Mauna Loa, Hawaii; Eldgja and Laki eruptions, Iceland; Springerville volcanic complex, Arizona; Taos Plateau volcanic complex, New Mexico; Lascar Volcano, Chile; Tatara-San Pedro volcanic complex, Chile; Patagonia slab window, Argentina) were selected with different tectonic environments, ages, and geochemistries and their rock magnetic properties including natural remanent magnetization (NRM), susceptibility, and hysteresis properties including coercivity were analyzed. Geochemical values were plotted as averages on a silica vs. alkali graph. There was some variation in NRM and susceptibility values for each of the terrestrial locations (such as Taos Plateau), but overall the averages are a good representation of average NRM and susceptibility. None of the samples studied displayed high remanence, high susceptibility, and high coercivity that would indicate stable single-domain magnetite. Although vastly different basalt origins were studied, an analog to the highly magnetized Martian crust was not found. There are three possibilities for this. 1) A basaltic terrestrial analog does exist, yet it was not included in this study. This is a very viable possibility since there are basalts all over the Earth each with a unique origin. 2) A basaltic terrestrial analog does not exist because although the rocks on Mars are basaltic, the global magnetic field that existed billions of years ago on Mars was unlike that of Earth. Recent work (Stanley et al, 2008) has shown that the Martian magnetic field might be completely different from Earth’s, and therefore a terrestrial analog would be impossible to find. 3) A basaltic terrestrial analog does not exist, but a terrestrial analog of a different rock type does exist. The assumption that the surface rocks on Mars – which are known to be mostly basaltic – are the carrier of the high magnetism. There is the possibility that the surface may be the origin of the magnetism, and in the areas of extremely high magnetism the rocks might locally be different. Also, it may not be the surface rocks that are exhibiting the magnetism. It may be buried highly magnetic rocks under a basalt lava flows. In addition to seeking out other basalts as terrestrial analogs for to the highly magnetized Martian rocks, it would also be worthwhile to investigate the possibility of a different magnetic field for Mars and what other terrestrial rocks could display such high magnetism billions of years after the termination of the Martian magnetic field.

碩士
銘傳大學
資訊傳播工程學系碩士班
106
Location-based services (LBS) are becoming increasingly important for mobile phone users. Indoor positioning technology research is also relatively increased. Indoor positioning technology includes infrared, ultrasound, ultra-wide frequency, radio frequency identification, but these applications have some problems to overcome. The common wireless indoor positioning is Wi-Fi and Bluetooth. There are some difficulties yet to solve, so that positioning accuracy or reliability is difficult to improve. In recent years, some studies try to use the magnetic field to assist the positioning. Because the intelligent phone has a magnetometer and accelerometer, the Earth's magnetic field is not change suddenly and the mobile phone with the magnetic field a magnetometer and accelerometer could indoor positioning easily. Therefore, this study explores the effectiveness of mobile phones in measuring the Earth's magnetic field and the differences in indoor positioning of different brands of mobile phones. The results show that the location of the Earth's magnetic field is not easy to change with time. Each location has its own magnetic field characteristics, it can be used as a reference for positioning. As for the measurement of the error between the phone can take the magnetic induction 1and its horizontal component ratio as a position feature to locate. Finally, by increasing the environmental conditions of the fixed travel direction and Landmark, the minimum error distance obtained is 3.59 meters. According to the result of positioning classification using different mobile phones, the best positioning accuracy is 71.3% (k-NN, k = 3).