This thesis describes the design and testing of a floppy disk drive based digital recorder. The device was originally built for a geomagnetic research project, but is also suitable for other phenomena with time scales from fractions of a second to approximately one day. The system is designed specifically to improve the reliability for long-term observing programs and to enhance the efficency of the subsequent data analysis procedures. Using an STD-Z80 BUS microcomputer, under the control of a Forth language program, the recorder stores digital data on removable 8-inch floppy disks. This thesis explicitly addresses the issue of cost and provides the necessary detail for reproduction of the device. A procedure is described for preparing the acquired data for analysis using computing facilities equiped with an appropriate disk reader. Also presented is a quantitative and qualitative evaluation of the recorder's performance when applied to both synthetic and natural signals. The latter include geomagnetically induced currents in power transmission lines. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Geomagnetically Induced Currents (GIC's) in B. C. Hydro's 500 kV transmission system have in the past been responsible for the generation of harmonics of 60 Hz, system voltage drops, and misoperation of relay units. Characterization of the associated magnetic storms' spatial scales would further the understanding of GIC generation in the area, and allow advanced warning of potential problems in future power transmission projects. Data collected in 1984 at four substations were analysed to determine lateral variations in geomagnetically induced earth surface electric fields. Inversion techniques were employed to find a variety of solutions that would reproduce the data. Results suggested that the magnetic storms were larger than the area monitored, and that resultant electric fields seen by a large portion of the transmission grid were uniform. Departures from this uniformity in other portions of the electric field models were felt either to be due to earth induction effects, or in some cases, to be artifacts of the data analysis techniques. An experiment designed to determine the controlling factors behind GIC's is outlined. Considerable effort would be required to explicitly determine all electric fields affecting the transmission system / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The purpose of the work reported here was to determine the feasibility of applying the nuclear induction technique of Bloch to the direct observation of nuclear magnetic resonance in the very weak magnetic field of the earth.

This Master's thesis deals with design of sensor network for synchronised low-level recording of changes in magnetic part of Earth's field in ELF band in multiple places. The goal is acquisition of changes due to solar storm activity, while taking into account, that in research of geomagnetic effects connected with solar events is spectrum of interest broader and reach up to VLF, where a solution is often made of combination of receivers in ELF and VLF, a decision was made, after consulting with thesis supervisor and researchers, that device will be designed for ELF, but can be easily modified, by changing preamplifier, for using in higher frequency bands, creating a solid founding for further measurements and research in this field.

No description available.

The ionosphere is of practical importance for satellite-based communication and navigation systems due to its variable refractive nature which affects the propagation of trans-ionospheric radio signals. This thesis reports on the first attempt to investigate the mechanisms responsible for the generation of positive ionospheric storm effects over mid-latitude South Africa. The storm response on 15 May 2005 was associated with equatorward neutral winds and the passage of travelling ionospheric disturbances (TIDs). The two TIDs reported in this thesis propagated with average velocities of ∼438 m/s and ∼515 m/s respectively. The velocity of the first TID (i.e. 438 m/s) is consistent with the velocities calculated in other studies for the same storm event. In a second case study, the positive storm enhancement on both 25 and 27 July 2004 lasted for more than 7 hours, and were classified as long-duration positive ionospheric storm effects. It has been suggested that the long-duration positive storm effects could have been caused by large-scale thermospheric wind circulation and enhanced equatorward neutral winds. These processes were in turn most likely to have been driven by enhanced and sustained energy input in the high-latitude ionosphere due to Joule heating and particle energy injection. This is evident by the prolonged high-level geomagnetic activity on both 25 and 27 July. This thesis also reports on the phase scintillation investigation at the South African Antarctic polar research station during solar minimum conditions. The multi-instrument approach that was used shows that the scintillation events were associated with auroral electron precipitation and that substorms play an essential role in the production of scintillation in the high latitudes. Furthermore, the investigation reveals that external energy injection into the ionosphere is necessary for the development of high-latitude irregularities which produce scintillation. Finally, this thesis highlights inadequate data resources as one of the major shortcomings to be addressed in order to fully understand and distinguish between the various ionospheric storm drivers over the Southern Africa mid-latitude region. The results presented in this thesis on the ionospheric response during geomagnetic storms provide essential information to direct further investigation aimed at developing this emerging field of study in South Africa.

This thesis is an account of the investigation into the physical nature of the proposed discontinuity in upper mantle conductivity in south eastern British Columbia responsible for the change in appearance of geomagnetic variations reported by Hyndman (1963). Variometer stations were established along two profiles, one east-west and one north-south, each several hundred kilometers in length. The geomagnetic records thus obtained are used to estimate the depth to a proposed highly conducting substratum. Parkinson diagrams are also derived for many stations on the profiles. The theoretical problem of magnetic induction in a 2-layer horizontally stratified half-space is solved. Theoretical expressions are derived for the attenuation of power in the vertical component of the earth's magnetic field relative to the two horizontal components as a function of frequency, conductivity, and thickness of the top layer. These theoretical curves are compared to data determined experimentally by power spectral analysis of geomagnetic records recorded at Crowsnest, Alberta, Lethbridge, Alberta; and Grand Forks, B.C. This analysis indicates Kootenay Lake to be near a region of anomalous induction in the earth. If the conductor is assumed to be two dimensional its strike appears to be magnetic east-west. The observed attenuation of the vertical component at stations west of Kootenay Lake relative to those of Kootenay Lake is accounted for in terms of the upheaval in the west of a highly conducting substratum. The analysis indicates a layer of conductivity 10⁻¹¹ e.m.u. rises to within 10 km. of the surface in the west while lying at a depth of 100 km. or more in the east. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Jurassic volcanic rocks in southeastern Arizona provide an opportunity to study the paleomagnetism of an autochthonous segment of the Mesozoic Cordilleran magmatic arc. The Corral Canyon sequence in the Patagonia Mountains is a 650 meter thick homoclinal sequence consisting of interbedded volcaniclastic red-beds, welded ash-flow tuff, and lavas. Rb/Sr isotopic analysis of eight whole rock tuff samples yields an isochron age of 171 ± 3 Ma. Welded tuffs in the Corral Canyon sequence possess a stable, primary magnetization carried in both magnetite and hematite that defines a paleomagnetic pole at 61.8°N, 116.0°E, alpha₉₅= 6.2°. This pole is considered to be a reliable Middle Jurassic reference pole for cratonic North America. Paleomagnetic study of the Canelo Hills volcanics welded tuff member also yields a stable, primary magnetization throughout a stratigraphic thickness of 600 meters. However, results from this formation are enigmatic and the mean pole is discordant with respect to Middle Jurassic reference poles. Various aspects of the paleomagnetic data indicate that discordance of the Canelo Hills volcanics pole is probably due to acquisition of remanent magnetization during a period of non-dipole behavior of the geomagnetic field. Dispersion of paleomagnetic directions suggests that the welded tuff member represents at most two cooling units and can be interpreted as a caldera-fill sequence. A revised Jurassic APW path differs significantly from available paths and has important implications for North American plate motion and paleolatitude. The spatio-temporal progression of reliable Jurassic paleopoles, in conjunction with Triassic and Early Cretaceous poles, is well described by paleomagnetic Euler pole analysis. The APW path is divided into three tracks, separated by two cusps. These cusps represent changes in the direction of North American absolute plate motion and can be correlated with global plate motion and intraplate deformation events at approximately 200-210 Ma and 150 Ma. Finally, the APW path presented herein predicts more southerly Late Triassic and Jurassic paleolatitudes for North America than have been suggested by previous authors. Using revised reference poles, there are no inclination anomalies within paleomagnetic data from Late Triassic and Early Jurassic rocks of Stikinia and Quesnellia (B.C., Canada).

Oriented archaeomagnetic samples were collected from 158 in situ features at 33 sites in the southwestern U.S. Seventy-three independently dated features were used for analysis of secular variation. A moving-window smoothing technique with outlier rejection was developed to objectively compute a virtual geomagnetic pole (VGP) path. Weighted Fisher statistics, accounting for errors in both dating and archaeomagnetic direction, were used to compute a mean VGP and standard error (A95) within each window of time. The VGP moves from 86°N, 83°E at A.D. 750 to 74°N, 192°E at A.D. 1075, and then to 85°N, 236°E at A.D. 1425. Secular variation of the VGP ranges from .00423-.350°/yr with a median of .0359°/yr. The A95s for the VGP curve range from 1.33-5.28°. Archaeomagnetic declinations and inclinations in Tucson range from 346-359°E and 47-60°. The close agreement with a similarly constructed VGP curve for Arkansas implies a small nondipole field in North America between A.D. 1150-1450. The VGP curve is significantly different from that of R. L. DuBois. Three case histories of archaeomagnetic dating suggest the validity of the new curve. The Thellier-Thellier paleointensity experiment was performed on 187 specimens from 77 potsherds. A significant magnetic fabric anisotropy, typically 30%, was found. Using an easy-plane model of magnetization, the anisotropy correction systematically increased the paleointensities by 5%. Paleointensities were interpreted for 127 samples from 54 sherds. All ceramics were independently dated and used along with other results to construct a virtual axial dipole moment (VADM) curve. A moving-window smoother using weighted statistics within each interval of time and incorporating outlier analysis was used. The Southwestern VADM at 300 B.C. is 14 x 10('22)Am('2), decreases to 8.6 x 10²²Am² at A.D. 800, and increases to 12.9 x 10²²Am² at A.D. 1500. Paleointensities from Hohokam ceramics compare favorably with paleointensities from other Southwestern ceramics, regardless of whether the long Hohokam chronology beginning at 300 B.C. or the short chronology beginning at A.D. 500 are used. There is also reasonable agreement between the Southwest and Mesoamerican VADM records.

The UK 2008 Climate Change Act transferred a global policy issue into national legislation, establishing unprecedented targets for reducing emissions justified by scientific evidence. The Act prompted a question: could such stretching targets be achieved? This question is addressed through an embedded case study within the East Midlands region between 2010-2011. The research makes an original contribution to knowledge, taking an interpretive, decentred approach to subnational climate policy implementation, focusing on the policy meanings created and acted upon during the introduction of the Cameron Government’s austerity and localism agendas. These meanings are recovered using a mix of conversational interviews and meeting observations with policy actors. Subnational climate policy met significant challenges in being translated into action, being seen as peripheral to local policy concerns. Managers attempted to ‘embed’ climate policy within local authority practice, but were met with resistance and passivity stemming from climate policy’s diverse meanings amongst policy actors. Performance management was important in symbolising rational policy-making, rather than for its instrumental effectiveness. This briefly raised the priority of climate policy, but where locally compelling political arguments for implementation were absent, programmes became vulnerable to budget cuts. With stronger local arguments focusing on kindred policy areas such as fuel poverty and reducing local authorities’ own energy use, vulnerability was reduced. Localism brought such arguments into focus, as regional partnerships weakened and the National Indicators performance management framework was removed. Responses to these developments highlighted how perceptions of the location and flow of power contributed to meaning construction. The shift to kindred policy aims brings into question the plausibility of climate change targets predicated on scientific evidence rather than local policy meanings. The endurance of local climate policy is explained as a policy myth, enabling short term continuity with the promise of longer term change.