Statistical evidence indicates that the positions of the moon, Mercury, and Venus affect magnetic activity frequency observed at the earth, and the position of the earth affects the frequency of blue clearings on Mars. This study shows that these effects may be explained as a result of the action of shock and bow waves formed by these bodies in the supersonically streaming interplanetary plasma. The attenuation of large kinetic energy variations in the streaming plasma behind such bodies is shown to be equal to the square of the ratio of the Mach number upstream to the Mach number downstream. For typical solar induced activity, this implies an attenuation coefficient of approximately 1/2 - 1/3. It is also shown that an activity increase is expected in the bow wave. The observational data fits a model with bow waves of Mach numbers 2.5 and 15 corresponding to the two bow waves predicted by the theory. The moon's effect varies from that of the planets in a manner that can be explained by its closeness to the magnetosphere. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

Four portable magnetometer stations were set up at intervals of 80 - 100 kilometers along an east-west profile running from Tofino on the west coast of Vancouver Island to Abbotsford on the mainland in order to study the spatial dependence of the coastal anomaly. These were supplemented by records from the permanent Victoria Magnetic Observatory. The Tofino-Abbotsford chain extends and partly overlaps an earlier chain of stations set up to search for geomagnetic anomalies, along an east-west profile from Lethbridge, Alberta to Vancouver, British Columbia, The coastal anomaly recorded at Tofino is observed exclusively in the vertical component, diminishing rapidly inland and reaching its maximum value when the inducing field changes in approximately an east-west direction with a frequency between one and two cycles per hour. The horizontal and vertical variations are in a ratio of two to one at the coast which is in agreement with induction ratios calculated at coastlines in Australia and California. The directional dependence and limited spatial extent of the anomaly indicate a rather shallow conductivity discontinuity, at most 100 kilometers deep, running approximately parallel to the continental shelfline. Since at the maximum response frequency the upper mantle beneath the ocean is largely shielded by the overlying wedge of sea water, the anomaly is thought to be mostly due to the conductivity contrast between the deep ocean and the continent. The diurnal geomagnetic variations which pass through the surface layers virtually unattenuated show at least a twenty five percent enhancement in the vertical component from Abbotsford to Tofino. This anomaly perhaps reflects a change in upper mantle conductivity more accurately than does the higher frequency Tofino anomaly. At a still higher frequency of three cycles per hour where the Tofino anomaly is already reduced, there is a small anomaly in the vertical component at Westham Island on the east side of Georgia Strait which is completely absent at lower frequencies. The influence of a shallow body of sea water such as Georgia Strait is expected to be small. Hence this anomaly is probably due to a conductivity structure beneath the Strait in the crust or upper mantle. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Starting from the dynamic equations of electromagnetics we derive mutual impedance formulas that include the effects of induced polarization (IP) and electromagnetic (EM) coupling. The mutual impedance formulas are given for four geometries: a fullspace, a cylinder in a fullspace, a halfspace, and a layer over a halfspace. IP effects are characterized by a Cole-Cole model, the properties of which are fully investigated. From the general mutual impedance formulas specific limiting forms are defined to characterize the IP and EM effects. Using these limiting forms a framework is developed to justify the addition or multiplication of the two effects. The additive and multiplicative models are compared in the cylinder and layer geometries with the conclusion that the additive model proves to be more accurate over a wider range of frequencies than the multiplicative model. The nature of the IP and EM effects is illustrated in all four geometries showing the effects of relevant parameters. In all cases it is shown that the real part of the mutual impedance contains important IP information that is less influenced by EM effects. Finally the effects of boundaries are illustrated by the cylinder and layer geometries and a theory is developed to incorporate EM effects and IP effects from multiple regions which utilizes frequency dependent real dilution factors. We also include a brief review of some EM "removal" schemes and dilution theory approximations.

No description available.

No description available.

Maps in pocket.

A thesis submitted to the faculty of science, University of the Witwatersrand, Johannesburg, In fulfilment of the requirements for the Degree of Doctor of Philosophy Johannesburg 1990 / The processing of near-earth satellite magnetometer data towards extracting an improved lithosphere anomaly map is addressed. The two aspects of the data reduction route where data quality has been compromised most by contemporary methods is researched, namely;[Abbreviated Abstract. Open document to view full version] / GR2017