Dimmock, Andrew (2012) The study of magnetic and electric field structures at planetary magnetospheres. PhD thesis, University of Sheffield.
The research of collisionless shocks is one of the fundamental areas of plasma physics research. One of the underlying problems of shock research is iden- tifying the relationship between upstream shock conditions and the param- eters of the shock front. However, the study of shocks can be limited by both the lack of data coverage during the shock transition, or the delicate interpretation of datasets at the shock front. Multi-spacecraft missions have been invaluable to the study of shock structure as they permit the separation of temporal and spatial variations at the shock front. Beyond the terrestrial environment only single spacecraft missions are available. The work presented overcomes this restriction using prior knowledge of shock structure and applies it to perform the first statis- tical study of the scales at the Venusian bow shock. The significant result from this was that the Venusian bow shock displays the same normalised scale and dependency on upstream parameters as the terrestrial shock despite no magnetic field and observation under variable solar wind conditions. One important parameter is the cross-shock potential. However, its estimation is complicated by the lack of full electric field data and its delicate interpreta- tion. A new method is proposed to reconstruct the full electric field vector at the quasi-perpendicular shock front. and study its relationship between the upstream shock parameters. The significant result was the decrease of nor- malised cross-shock potential with the increasing Mach number which agrees with analytical studies. The role of dispersion mechanisms in the form of upstream waves is also a crucial process which balances the shock front and prevents overturning. A case study is presented which identifies nonlinear whistler waves transporting energy away form the shock front. Their role, generation mechanism and effect on shock formation are discussed.
|Item Type:||Thesis (PhD)|
|Department:||The University of Sheffield > Faculty of Engineering (Sheffield) > Automatic Control and Systems Engineering (Sheffield)|
|Deposited By:||Mr Andrew Dimmock|
|Deposited On:||08 Oct 2012 15:23|
|Last Modified:||08 Oct 2012 15:23|
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