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Archaeomagnetism is an area of research that utilises the magnetic properties of archaeological materials to date past human activity. This research aimed to use the evidence of past geomagnetism, as recorded by archaeological and geological materials, to identify and characterise short timescale changes in the Earth¿s magnetic field. This contribution to the discipline focused on the first millennium BC, as there is evidence that during this time the Earth¿s magnetic field experienced rapid changes in direction. This work focused on an established weakness in archaeomagnetic studies, i.e. the application of archaeological information to assign a date range to the magnetic directions. The date ranges for 232 magnetic directions from 98 Iron Age sites were reviewed and a programme of fieldwork produced 25 new magnetic directions from 11 Iron Age sites across Britain. The approach developed in this thesis has made significant improvements to the data examined, which represent the prehistoric section of the British secular variation curve (SVC). These data have been incorporated into the British archaeomagnetic dataset that now comprises over 1000 magnetic directions and will be used to generate future British SVCs. The potential of the near continuous records of geomagnetic secular variation from British lake sediment sequences to SVCs was explored. This showed that these sediments have recorded the relative changes in the Earth¿s magnetic field but the dating and method of constructing the British master curve requires revision. As SVCs are predominately used as calibration curves for archaeomagnetic dating, this work provides a foundation for a revised and extended British SVC. This revision would be to the mutual benefit of studies in archaeology and archaeomagnetism, as the latter could potentially enable highresolution dating of Iron Age material, providing a viable alternative to radiocarbon dating. / Available full-text since June 30th 2013, at the end of the embargo period. / Lab data and appendices 3 and 4 are unavailable online.

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Yes / Archaeomagnetic dating offers a valuable chronological tool for archaeological investigations, particularly for dating fired material. The method depends on the establishment of a dated record of secular variation of the Earth's magnetic field and this paper presents new and updated archaeomagnetic directional data from the UK and geomagnetic secular variation curves arising from them. The data are taken from publications from the 1950's to the present day; 422 dated entries derived from existing archaeo and geomagnetic databases are re-evaluated and 487 new directions added, resulting in 909 entries with corresponding dates, the largest collection of dated archaeomagnetic directions from a single country. An approach to improving the largest source of uncertainty, the independent dating, is proposed and applied to the British Iron Age, resulting in 145 directions from currently available databases being updated with revised ages and/or uncertainties, and a large scale reassessment of age assignments prior to inclusion into the Magnetic Moments of the Past and GEOMAGIA50 databases. From the significantly improved dataset a new archaeomagnetic dating curve for the UK is derived through the development of a temporally continuous geomagnetic field model, and is compared with previous UK archaeomagnetic dating curves and global field models. The new model, ARCH-UK.1 allows model predictions for any location in the UK with associated uncertainties. It is shown to improve precision and accuracy in archaeomagnetic dating, and to provide new insight into past geomagnetic field changes. / Arts and Humanities Research Council

Os diversos fenômenos solares mostram que a sua atividade não é constante, sendo as manchas solares observadas em sua fotosfera um indicador de atividade do Sol. Os números dessas manchas seguem um ciclo de 11 anos que alterna entre máximos e mínimos; quanto maior o número de manchas, maior o número de erupções no Sol. A literatura médica vem mostrando algumas evidências de que a atividade solar possui alguma relação com a predisposição das pessoas a algumas doenças. As tempestades geomagnéticas são associadas a doenças cardiovasculares, mudanças na pressão arterial sistólica, gravidade da crise de enxaqueca, distúrbios psiquiátricos. As condições da atividade geomagnética são classificadas segundo Batista (2003) em uma escala de Calma, Transição, Ativo, Tempestade fraca, Tempestade intensa ou Tempestade muito intensa. No presente projeto de pesquisa, objetiva-se investigar a associação entre atividade geomagnética e internações diárias por infarto nos hospitais de Ribeirão Preto e região, no período de 1998 a 2007. A hipótese em estudo é que em dias de condições de atividade geomagnética muito perturbada, o número médio de internações por doenças isquêmicas do coração é maior. Para a análise dos dados foi utilizado o modelo de regressão de Poisson com função logarítmica com o auxílio do software SAS 9.2, utilizando o procedimento PROC GENMOD. Observa-se que há evidências de associação entre tempestades geomagnéticas e internações por IAM. / Numerous solar phenomena demonstrate that their activities are not continual, and sunspots noticed in their photosphere are considered an indicator by Suns activity. Numbers linked with these sunspots follow an eleven-year cycle, which alternates between high and low, it means, the greater the number of sunspots, the greater the number of Sun eruptions. Medical Literature has produced evidences that solar activity has some association with people predisposing to some diseases. Geomagnetic storms are related with cardiovascular disease, changes in systolic blood pressure, severity and psychiatric disorders. According to Batista (2003), geomagnetic activity conditions are categorized on a scale of Quiet, Transition, Acting, Weak Storm, Intense Storm or Very Intense Storm. This study intends to investigate the association between geomagnetic activity and daily hospitalization by acute myocardial infarction (AMI) in Ribeirão Preto and its region from 1998 to 2007. The hypothesis being studied is that: day which has unquiet geomagnetic condition, the average number of hospitalizations originated by ischemic heart disease is higher. In order to get on with data analysis, it was used Poissons regression model, with logarithmic function through SAS 9.2, using PROC GENMOD procedure. In consequence, it is observed that there are evidences between geomagnetic storms and hospitalizations by AMI.

O campo magnético da Terra varia em diferentes escalas de tempo, de milissegundos a bilhões de anos. Os dados de observatórios magnéticos e satélites obtidos nos últimos 150 anos indicam que o momento do dipolo magnético terrestre está diminuindo continuamente. Essa queda está associada à presença de fontes não-dipolares do campo em uma extensa região que abrange todo o Atlântico Sul e uma porção da América do Sul, sendo que no Brasil a contribuição dessas fontes varia fortemente com a latitude. Em escala de tempo arqueomagnética (~1.000-10.000 anos) a evolução do campo magnético terrestre não é tão bem estabelecida, principalmente em função da escassez de dados no hemisfério Sul, que contribui com apenas 5% dos dados de intensidade obtidos para os últimos 4.000 anos. A América do Sul, com alguns poucos resultados no Peru, Equador e Bolívia, pode ser considerada a terra incógnita da arqueointensidade. Nesta tese são apresentados os primeiros resultados arqueomagnéticos para o território brasileiro. Foram escolhidas duas regiões de estudo, o Nordeste e o Sudeste do Brasil, situadas em diferentes faixas de latitude de modo a investigar diferentes contribuições de componentes não-dipolares do campo. No Nordeste, as amostras foram coletadas na cidade de Salvador (BA), a primeira capital do Brasil, fundada em 1549 AD. Na região Sudeste a amostragem foi efetuada nas cidades de Anchieta (ES), Rio de Janeiro (RJ), Niterói (RJ), Iperó (SP), Piracicaba (SP) e Botucatu (SP). Nas duas regiões, a paleointensidade do campo magnético terrestre foi obtida em materiais construtivos (tijolos e alguns fragmentos de telhas) datados entre 1550 AD e 1920 AD. As idades desses materiais foram estabelecidas com base em estudos arqueológicos e registros históricos das construções, fornecendo incertezas inferiores a 30 anos para a grande maioria das amostras. As paleointensidades foram estimadas utilizando-se dois métodos: (a) duplo aquecimento com medidas em temperatura ambiente, pelo protocolo de Thellier modificado por Coe; (b) duplo aquecimento com medidas contínuas em alta temperatura, pelo protocolo Triaxe. Após as medidas e correções magnéticas, todas as amostras foram analisadas com base em rigorosos critérios de seleção, que resultaram em 23 novas determinações de intensidade de alta qualidade (correspondendo a um total de 584 espécimes analisados, com uma taxa de sucesso de 57%). A partir desses resultados foram traçadas duas curvas de variação da intensidade do campo magnético para cada uma das regiões estudadas, abrangendo os últimos 500 anos. Essas curvas revelam uma oscilação do momento de dipolo nos últimos cinco séculos, que não foi prevista nos modelos de campo disponíveis atualmente, trazendo implicações importantes no entendimento da evolução dos campos dipolar e não-dipolar nessa escala de tempo. As variações rápidas descritas nessas curvas permitem aplicar o arqueomagnetismo como ferramenta de datação arqueológica, como exemplificado pela datação de uma casa do Pelourinho em Salvador. / The Earth\'s magnetic field varies in different timescales, from milliseconds to billions of years. Magnetic data from observatories and satellites indicate that the dipole moment has continuously been decreasing for the past 150 years. This decay is associated to the presence of non-dipole sources covering a wide region that encompasses the South Atlantic and part of South America; in Brazil, the contribution of the non-dipole fields varies strongly with latitude. In the archeomagnetic timescale (~1,000-10,000 years), the evolution of the Earth\'s magnetic field is not well established, mainly due to the scarcity of data from southern hemisphere, which contributes with only 5% of the intensity data for the past 4,000 years. South America is the terra incognita of archeointensity, counting only a handful of results from Peru, Ecuador and Bolivia. This thesis presents the first archeomagnetic results from Brazil. In order to investigate different contributions of non-dipolar sources, we concentrated our sampling in two regions located in different latitudes the Northeast and Southeast regions of Brazil. In the Northeast region, all samples were collected in the city of Salvador (BA), the first Brazilian capital settled in 1549 AD. In the Southeast region, sampling was conducted in the cities of Anchieta (ES), Rio de Janeiro (RJ), Niterói (RJ), Iperó (SP), Piracicaba (SP) and Botucatu (SP). All paleointensity data was obtained from architectural fragments (bricks and some tiles) dated between 1550 AD and 1920 AD. The age of bricks and tiles was established on the basis of archeological studies and the historical record of the buildings, providing age uncertainties of less than 30 years for most of the samples. Paleointensity estimates were obtained by two methods: (a) double-heating with measurements in room temperature, using the modified version of the Thellier protocol; (b) double-heating with measurements in high temperatures, using the Triaxe protocol. After measurements and magnetic corrections, all samples were screened using strict selection criteria resulting in 23 high-quality new site-mean intensity values (from 584 analyzed specimens, with a success rate of 57%). These results were integrated into two curves of geomagnetic intensity variation for each studied region over the past five centuries. These curves reveal an oscillating dipole moment for the past five centuries, a behavior not predicted in currently available geomagnetic field models, thus providing key information on the dipole and non-dipole field evolutions in this timescale. The rapid intensity changes described in these curves permit the application of archeointensity techniques as an archeological dating tool, as exemplified by the dating of a house from the Pelourinho area, in Salvador city.

Os diversos fenômenos solares mostram que a sua atividade não é constante, sendo as manchas solares observadas em sua fotosfera um indicador de atividade do Sol. Os números dessas manchas seguem um ciclo de 11 anos que alterna entre máximos e mínimos; quanto maior o número de manchas, maior o número de erupções no Sol. A literatura médica vem mostrando algumas evidências de que a atividade solar possui alguma relação com a predisposição das pessoas a algumas doenças. As tempestades geomagnéticas são associadas a doenças cardiovasculares, mudanças na pressão arterial sistólica, gravidade da crise de enxaqueca, distúrbios psiquiátricos. As condições da atividade geomagnética são classificadas segundo Batista (2003) em uma escala de Calma, Transição, Ativo, Tempestade fraca, Tempestade intensa ou Tempestade muito intensa. No presente projeto de pesquisa, objetiva-se investigar a associação entre atividade geomagnética e internações diárias por infarto nos hospitais de Ribeirão Preto e região, no período de 1998 a 2007. A hipótese em estudo é que em dias de condições de atividade geomagnética muito perturbada, o número médio de internações por doenças isquêmicas do coração é maior. Para a análise dos dados foi utilizado o modelo de regressão de Poisson com função logarítmica com o auxílio do software SAS 9.2, utilizando o procedimento PROC GENMOD. Observa-se que há evidências de associação entre tempestades geomagnéticas e internações por IAM. / Numerous solar phenomena demonstrate that their activities are not continual, and sunspots noticed in their photosphere are considered an indicator by Suns activity. Numbers linked with these sunspots follow an eleven-year cycle, which alternates between high and low, it means, the greater the number of sunspots, the greater the number of Sun eruptions. Medical Literature has produced evidences that solar activity has some association with people predisposing to some diseases. Geomagnetic storms are related with cardiovascular disease, changes in systolic blood pressure, severity and psychiatric disorders. According to Batista (2003), geomagnetic activity conditions are categorized on a scale of Quiet, Transition, Acting, Weak Storm, Intense Storm or Very Intense Storm. This study intends to investigate the association between geomagnetic activity and daily hospitalization by acute myocardial infarction (AMI) in Ribeirão Preto and its region from 1998 to 2007. The hypothesis being studied is that: day which has unquiet geomagnetic condition, the average number of hospitalizations originated by ischemic heart disease is higher. In order to get on with data analysis, it was used Poissons regression model, with logarithmic function through SAS 9.2, using PROC GENMOD procedure. In consequence, it is observed that there are evidences between geomagnetic storms and hospitalizations by AMI.

The goal of this work was to compensate for the effects of the Earth’s magnetic field in a vector field magnetic sensor. The magnetic sensor is a part of a low-cost crash avoidance system by Stephane Roussel where the magnetic sensor was used to detect cars passing when it was mounted to a test vehicle. However, the magnetic sensor’s output voltage varied when it changed orientation with respect to the Earth’s magnetic field. This limited the previous work to only analyze detection rates when the test vehicle travelled a single heading. Since one of the goals of this system is to be low-cost, the proposed solution for geomagnetic compensation will only use a single magnetic sensor and a consumer-grade GPS. Other solutions exist for geomagnetic compensation but use extra sensors and can become costly. In order to progress the development of this project into a commercial project, three separate geomagnetic compensation algorithms and a calibration procedure were developed. The calibration procedure compensated for the local magnetic field when the magnetic sensor was mounted to the test vehicle and allowed for consistent magnetic sensor voltage output regardless of the type of test vehicle. The first algorithm, Compensation Scheme 1 (CS1), characterized the local geomagnetic field with a mathematical function from field calibration data. The GPS heading was used as the input and the output is the voltage level of the Earth’s magnetic field. The second algorithm, Compensation Scheme 1.5, used a mathematical model of the Earth’s magnetic field using the International Geomagnetic Reference Field. An algorithm was developed to take GPS coordinates as an input and output the voltage contributed by the mathematical representation of the Earth’s magnetic field. The output voltages from CS1 and CS1.5 were subtracted from the calibrated magnetic sensor data. The third algorithm, Compensation Scheme 2 (CS2), used a high pass filter to compensate for changes of orientation of the magnetic sensor. All three algorithms were successful in compensating for the geomagnetic field and vehicle detection in multiple car headings was possible. Since the goal of the magnetic sensor is to detect vehicles, vehicle detection rates were used to evaluate the effectiveness of the algorithms. The individual algorithms had limitations when used to detect passing cars. Through testing, it was found that CS1 and CS1.5 algorithms were suitable to detect vehicles while stopped in traffic while the CS2 algorithm was suitable vehicle detection while the test vehicle is moving. In order to compensate for the limitations of the individual algorithms, a fused algorithm was developed that used a combination of CS1 and CS2 or CS1.5 and CS2. The vehicle speed was used in order to determine which algorithm to use in order to detect cars. Although the goal of this project is not vehicle detection, the rate of successful vehicle detection was used in order to evaluate the algorithms. The evaluation of the fused algorithm demonstrated the value of using CS1 and CS1.5 to detect vehicles when stopped in traffic, which CS2 algorithm cannot do. For a study conducted in traffic, using the fused algorithm increased vehicle detection rates by 51%-62% from using the CS2 algorithm alone. Since this work successfully compensated for geomagnetic effects of the magnetic sensor, the low-cost crash avoidance system can be further developed since it is no longer limited to driving in a single direction. Other projects that experience unwanted geomagnetic effects in their projects can also implement the knowledge and solutions used in this work.

<p>Three long sediment cores (BDP-98 – 600 m, BDP-96 – 200 m and BDP-93 – 100 m) drilled in Lake Baikal (Siberia) have been studied with the aims of establishing an absolute chronology and reconstructing paleoclimatic and paleoenvironmental changes in the region. The location of the lake at relatively high latitude and continental interior and a thick continuous sedimentary archive that developed in a rift system tectonic setting provide unique material for this investigation. The cosmogenic isotope ¹⁰Be was used for dating and the results indicate time spans of 8 (+0.8\-0.6) Myr for BDP-98, 5.5 (±0.13) Myr for BDP-96 and >0.7 Myr for BDP-93. Two major sedimentary facies (deltaic and hemipelagic) are distinguished by textural geochemical and mineralogical data. Detrital mineral composition suggests negligible change in provenance during the period studied. Formation of authigenic minerals, such as framboidal pyrite, vivianite and siderite, reflects variable environmental conditions in the lake and climate change in the region. Biogenic silica content shows climatic influence, which is modified by the supply of detrital material and postdepositional alterations. ¹⁰Be dating, combined with lithological analysis of the sediments, makes it possible to place temporal constrains on climate cooling at the Miocene/Pliocene boundary (5 Myr ago) and at the Early/Late Pliocene boundary (3.6 Myr ago) as well as the beginning of the northern hemisphere glaciation at about 2.5–2.6 Myr ago. The regional east-west tectonic extension of south-east Asia, related to Tibetan Plateau uplift, was confined in the Baikal area to between about 7 and 5 Myr ago, with a rifting rate calculated at 7 mm year^-1. Furthermore, the ¹⁰Be data suggest that geomagnetic field intensity strengthened around the Miocene/Pliocene boundary.</p>

Three long sediment cores (BDP-98 – 600 m, BDP-96 – 200 m and BDP-93 – 100 m) drilled in Lake Baikal (Siberia) have been studied with the aims of establishing an absolute chronology and reconstructing paleoclimatic and paleoenvironmental changes in the region. The location of the lake at relatively high latitude and continental interior and a thick continuous sedimentary archive that developed in a rift system tectonic setting provide unique material for this investigation. The cosmogenic isotope 10Be was used for dating and the results indicate time spans of 8 (+0.8\-0.6) Myr for BDP-98, 5.5 (±0.13) Myr for BDP-96 and &gt;0.7 Myr for BDP-93. Two major sedimentary facies (deltaic and hemipelagic) are distinguished by textural geochemical and mineralogical data. Detrital mineral composition suggests negligible change in provenance during the period studied. Formation of authigenic minerals, such as framboidal pyrite, vivianite and siderite, reflects variable environmental conditions in the lake and climate change in the region. Biogenic silica content shows climatic influence, which is modified by the supply of detrital material and postdepositional alterations. 10Be dating, combined with lithological analysis of the sediments, makes it possible to place temporal constrains on climate cooling at the Miocene/Pliocene boundary (5 Myr ago) and at the Early/Late Pliocene boundary (3.6 Myr ago) as well as the beginning of the northern hemisphere glaciation at about 2.5–2.6 Myr ago. The regional east-west tectonic extension of south-east Asia, related to Tibetan Plateau uplift, was confined in the Baikal area to between about 7 and 5 Myr ago, with a rifting rate calculated at 7 mm year-1. Furthermore, the 10Be data suggest that geomagnetic field intensity strengthened around the Miocene/Pliocene boundary.