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dc.contributor.advisorDe Moortel, Ineke
dc.contributor.advisorMcClements, Ken G.
dc.contributor.authorThrelfall, James W.
dc.description.abstractIn this thesis the effect of the Hall term in the generalised Ohm’s law on Alfvén (shear) and fast wave propagation and dissipation in the ion cyclotron frequency range is investigated. The damping of an initially Gaussian field perturbation in a uniform Hall MHD plasma is treated analytically. Subsequently a 2D Lagrangian remap code (Lare2d) is used to study the damping and phase mixing of initially Gaussian field perturbations and a harmonic series of boundary-driven perturbations in a uniform field (in the presence of a transverse equilibrium density gradient). The same code is then used to study a range of initially shear and fast-wave perturbations in the vicinity of a magnetic X-type null point. The magnetic energy associated with an initially Gaussian field perturbation in a uniform resistive plasma is shown to decay algebraically at a rate that is unaffected by the Hall term to leading order in kδ where k is wavenumber and δ is ion skin depth. A similar decay law applies to whistler perturbations in the limit kδ>>>1. We demonstrate that in both geometries considered, the inclusion of the Hall term reduces the effectiveness of phase-mixing in plasma heating. The reduction in the damping rate in the uniform field (non-uniform density) cases, arising from dispersive effects, tends to zero in both the weak and strong phase mixing limits. In the Hall MHD X-point case, minimal reductions are seen for initially shear wave pulses, suggesting that little or no phase-mixing takes place. Nonlinear fast wave pulses which interact with the initial X-point destabilise the local field sufficiently to generate multiple null pairs; subsequent oscillatory current sheet behaviour appears unaffected by earlier differences between the MHD and Hall MHD cases.en_US
dc.publisherUniversity of St Andrews
dc.subjectMagnetohydrodynamics (MHD)en_US
dc.subjectMagnetic reconnectionen_US
dc.subjectPhase mixingen_US
dc.subjectTwo-fluid theoryen_US
dc.subject.lcshPlasma (Ionized gases)--Mathematical modelsen_US
dc.subject.lcshMagnetic reconnectionen_US
dc.subject.lcshSun--Corona--Mathematical modelsen_US
dc.titleWave propagation, phase mixing and dissipation in Hall MHDen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US
dc.publisher.departmentCulham Centre for Fusion Energyen_US

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