This diploma thesis deals with selection, construction and realization of measuring device of magnetostatic field and description of the basic laws used in magnetism. It also describes principles and functions of particular sensors and probes curently used for measuring of magnetic fields, especially fluxgate magnetometer, which has been constructed. The result of this work is a particular realisation of measuring device with functional testing measurements.

Banded iron formations (BIFs) are iron oxide- and silica-rich chemical sedimentary rocks and the principal source of high-grade (HG) iron ore. Magnetic survey methods are commonly applied in the exploration for BIF-hosted iron ore deposits but the interpretation of total magnetic intensity (TMI) data is often complicated by the presence of strong remanent magnetization and anisotropy of magnetic susceptibility (AMS). This study evaluated a tri-axial fluxgate vector magnetometer system for ground-based high-resolution mapping of BIF-hosted HG iron ore deposits at a 16 ha site near Mary River, Baffin Island. Magnetometer orientation was measured using a MEMS (Micro Electro-Mechanical System) accelerometer and dual D-GPS receivers. 12-oriented block samples were collected for analysis of rock magnetic properties and supplemented with outcrop measurements using a hand-held susceptibility probe. The large (3 Gauss) dynamic range of the tri-axial vector magnetometer permitted mapping of HG magnetite ore zones, with TMI in excess of 400,000 nT. A 20 m-wide W-E trending HG zone and a narrow (<10 m) BIF zone were identified in RMV maps with distinctive dipole signatures. Within the HG zone a northwest-southeast oriented magnetic fabric was defined by linear magnetic lows that offset the strike of the HG ore zone and were interpreted as brittle faults or shear zones. The RMV orientation indicated the presence of strong bedding parallel magnetization, while its signal amplitude showed a wide variation between ore types and provided basis for ore grade differentiation. Paleomagnetic measurements revealed high Q ratios for hematite ores and strong AMS for BIF. The results from Mary River demonstrate that remanence and AMS effects are important in BIF-hosted iron ores and cannot be neglected in magnetic interpretation and inversion modelling of magnetic source bodies. / Thesis / Master of Science (MSc)

no / This Short Report summarizes some initial results using real time GPS to navigate and collect magnetometer data using Foerster sensors and a magnetic cart. The Foerster system is primarily aimed at the detection of buried ordnance and, by comparison to some other magnetometer sensors, the reported sensitivity is relatively low. However, the sensors require no alignment in the field, nor does the system require a regular contiguous grid to be established across the survey area. The latter means that data grids of different sizes and orientation can be measured and stitched together as part of data restoration prior to processing. The accurate positioning of the data means that `staggering¿, which is often seen in time-based collection strategies, is not apparent in the data; overall less processing is required to produce a final image than is required for other fluxgate instruments. Data from a survey at Cyrene are reproduced to illustrate the strengths of the system

Earth is under constant influence of the Sun and phenomena driven by the solar wind that may affect man-made technology. These events are summarized under the concept of space weather. This creates variations in Earth’s magnetic field and nearby space. Space weather can affect power grids, gas pipelines and also have effects on human health. Due to these effects, as well as the scientific interest in space and the growing space industry, the need to monitor space weather, the space environment and how Earth is affected by them increases. Accurate magnetic mesurements rely on expensive magnetometers and careful calibration. Swedish Institute of Space Physics IRF, operates two magnetometers in Sweden, one observatory and one variometer to measure local geomagnetic variations. For the purpose of space weather, measurements of local variations have high demands on temporal resolution and precision but not the same need for long-term accuracy. The purpose of this thesis is to define and evaluate an autonomous system for local geomagnetic variations, with future hopes of creating a network of systems for space weather monitoring. The future goal is to be able to place systems in remote locations where they will be able to conduct measurements autonomously. The work was done by analysis and testing of a fluxgate magnetometer that was placed close to one of the IRFs existing magnetometers. Using data from the existing station as a reference, an analysis of the magnetometer could be performed. The results showed that the tested magnetometer had less precision than the existing station but could within a certain frequency range provide good results that make it possible to measure the local geomagnetic variations that may be of use for space weather. Conclusions from this study show that it is possible to create a simpler autonomous system for measurements of the local geomagnetic variations, but that this system requires further development, where future work can be based on this degree project as a basis. / Jorden är under konstant påverkan av solen och fenomen drivna av solvinden som kan påverka mänsklig teknologi. Dessa event sammanfattas under begreppet rymdväder. Genom detta skapas variationer i Jordens magnetfält och närliggande rymd. Rymdväder kan påverka kraftnät, gasledningar och även ha effekter på mänsklig hälsa. På grund av dessa effekter samt det vetenskapliga intresset för rymden och den växande rymdbranschen ökar behovet av att övervaka rymdväder, rymdmiljön samt hur Jorden påverkas av de. Exakta magnetiska mätningar är beroende av dyra magnetometrar och nogrann kalibrering. Institutet för Rymdfysik IRF driver två magnetometrar i Sverige, ett observatorium och en variometer för att mäta lokala geomagnetiska variationer. Då mätningar av lokala variationer har höga krav på temporal upplösning och precision men inte samma behov av kontroll på långsiktig noggrannhet. Syftet med det här examensarbetet är att definiera och utvärdera ett autonomt system för lokala geomagnetiska variationer, med framtida förhoppningar om att skapa ett nätverk av system för övervakning av rymdväder. Framtidsmålet är att kunna placera ut system på avlägsna platser där det autonomt ska kunna bedrivas mätningar. Arbetet gjordes genom analys och tester med en fluxgate-magnetometer som placerades i närheten av en av IRF befintliga magnetometrar. Med data från den existerande stationen som referens kunde en analys av magnetometern utföras. Resultatet visade att den testade magnetometern hade mindre precision än den befintliga stationen men kunde inom ett viss frekvensspann förse goda resultat som gjorde det möjligt att mäta de lokala geomagnetiska variationerna som kan vara till nytta för rymdväder. Slutsatser från denna studie visar att det är möjligt att skapa ett enklare autonomt system för mätningar av de lokala geomagnetiska variationerna men att detta system kräver vidare utveckling, där framtida arbete kan utgå från resultaten som erhölls i detta examensarbete.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Geomagnetic storms are primarily driven by the rapid transfer of energy from the solar wind to the magnetosphere. The mechanism of energy transfer involves the merging of the interplanetary magnetic field to the geomagnetic field in a process known as magnetic reconnection. This leads to an influx of energetic, charged particles into the magnetosphere so that current systems are enhanced. Specifically, an increase in the equatorial ring current leads to a decrease in the surface field. Geomagnetic storms are thus characterized by a strong decline in the horizontal components of the geomagnetic field, lasting from several hours to days. The intensity of a storm is described by the disturbed storm-time index, which is essentially a measure of the deviation from the typical quiet day variation along the equator. Severe storms can lead to the disruption of high frequency (HF) communications as a consequence of a strongly perturbed ionosphere. By the same token, the global positioning system (GPS) can become highly unreliable during magnetically disturbed conditions, yielding distance errors as large as 50 meters. The impact of geomagnetic activity and other solar-driven processes on technology systems are collectively known as space weather. Magnetic field sensing thus forms an important part of space weather forecasting and is vital to space science research as a means of improving our understanding of solar wind-magnetosphere interactions. This study examines the use of magnetometers built as SQUIDs (Superconducting Quantum Interference Devices) for monitoring the geomagnetic field for space weather forecasting purposes. A basic theory of superconductivity is presented and subsequently the key aspects governing the operation of SQUIDs are discussed. Space weather is also introduced with respect to the various processes on the sun that perturb the magnetosphere and hence the geomagnetic field. The method of analysis was basically to Fourier-transform the data using the Wiener-Khintchine theorem. A systematic approach to Fourier analysis is thus presented, demonstrating the superiority of the Wiener-Khintchine theorem in noise reduction. The suitability of SQUID magnetometers for space science research is demonstrated by a comparative study between SQUID and fluxgate datasets for magnetic storms during 2011. Strong correlation was observed between the frequency content of the SQUID and fluxgate signals. This result supports South Africa’s SQUID project, currently undertaken as a collaborative effort between SANSA Space Science and the Department of Electrical and Electronic Engineering at Stellenbosch University. This thesis thus lays a foundation for future research involving advanced magnetometry using SQUIDs. / AFRIKAANSE OPSOMMING: Geomagnetiese storms word hoofsaaklik gedryf deur die vinnige oordrag van energie van die sonwind na die magnetosfeer. Die meganisme van energie oordrag behels die samesmelting van die interplanetêre magneetveld met die geomagneetveld, in 'n proses wat bekend staan as magnetiese heraansluiting. Dit lei tot 'n instroming van energieke elektries-gelaaide deeltjies, tot in die magnetosfeer, met die gevolg dat magnetosferiese elektriese stroomstelsels versterk word. 'n Toename in die ekwatoriale ringstrome lei spesifiek tot 'n afname in die horisontale komponent van die geomagnetiese veld. Geomagnetiese storms word dus gekenmerk deur 'n sterk afname in die horisontale komponent van die geomagnetiese veld, ‘n afname wat etlike ure tot dae kan duur. Die intensiteit van 'n storm word beskryf deur die storm-tyd versteurings indeks , 'n maatstaf van die afwyking van die tipiese stil dag magnetiese variasie langs die ewenaar. Ernstige storms kan lei tot die ontwrigting van hoë frekwensie (HF) kommunikasie as 'n gevolg van 'n erg versteurde ionosfeer. Soortgelyk kan die Globale Posisionering Stelsel (GPS) hoogs onbetroubaar word tydens magneties versteurde toestande, en posisiefoute so groot as 50 meter veroorsaak. Die impak van geomagnetiese aktiwiteit en ander sonkrag gedrewe prosesse op tegnologie is gesamentlik bekend as ruimteweer. Magneetveldmetinge vorm dus 'n belangrike deel van ruimteweervoorspelling en is noodsaaklik vir ruimtewetenskaplike navorsing as 'n middel om die sonwind-magnetosfeer interaksies beter te verstaan. Hierdie studie ondersoek die gebruik van SQUID (Engels: Superconducting Quantum Interference Device) magnetometers vir die monitering van die geomagnetiese veld vir ruimteweervoorspellingsdoeleindes. ’n Basiese teorie van supergeleiding word aangebied, waarvolgens die sleutelaspekte van SQUIDs bespreek word. Ruimteweer word ook voorgestel in terme van die verskillende prosesse op die son wat die aarde se magnetosfeer en dus die geomagnetiese veld versteur. Die analisemetode wat hier gebruik word, is om die Fourier-transform van data met die Wiener-Khintchine theorema te bereken. A sistematiese metode vir Fourier-analise word aangebied, wat die superiorireit van die Wiener-Khintchine teorema vir ruisvermindering demonstreer. Die geskiktheid van SQUID magnetometers vir ruimtewetenskaplike navorsing word gedemonstreer deur ’n vergelykende studie tussen SQUID- en vloedhek-datastelle vir magnetiese storms gedurende 2011. Sterk korrelasie is waargeneem tussen die frekwensie-inhoud van die SQUID- en vloedhekseine. Hierdie resultate ondersteun Suid-Afrika se SQUID-projek, wat tans as ’n samewerkingspoging tussen SANSA Space Science en die Departement Elektriese en Elektroniese Ingenieurswese aan die Universiteit van Stellenbosch bedryf word. Hierdie tesis lê ’n fondasie vir toekomstige navorsing oor gevorderde magnetometrie met SQUIDs.