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Title: MHD Modes in Structured Magnetic Waveguides
Author: Carter, Ben
ISNI:       0000 0001 3522 4694
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2007
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In this Thesis the theoretical aspects of MHD wave modes in structured magnetic fields are studied. In particular the complication of a simple magnetic tube to include a transitionallayer and also to include twist is investigated. Solar observations have shown that the magnetic field on the Sun is far from simple and that wave guides occur in a vast array of different structures. More recent interpretations of observations have also indicated at a sub-structure to magnetic flux tubes for which current instruments do not yet have the resolution to image directly. It is proposed that such a flux tube could contain a sub-structure modelled by a magnetic cylinder in the form ofa magnetic core and magnetic annulus. The dispersion relations are found for a purely straight configuration and also for the case when the magnetic field is twisted. The modes of oscillation are investigated with specific attention given to the effect ofthe additional layer and to that of the twist on the existing modes. It is found that the change iJ? geometry of the magnetic flux tube has a marked effect on both the existence and on the phase speed of different modes. The introduction of an annulus layer increases the number of surface modes that exist and an applied twist gives rise to an infinite set of body modes and also transforms the behaviour of the surface modes, now having a dual nature - body or surface depending on wavelength. Short and long wav'e1ength analytical solutions are· sought providing further insight into the role ofmagnetic structuring in a flux tube.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available