Modelling anisotropic viscosity with applications in the solar corona

Quinn, James (2021) Modelling anisotropic viscosity with applications in the solar corona. PhD thesis, University of Glasgow.

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Abstract

The dissipation of kinetic energy through viscosity provides one mechanism by which the solar atmosphere may be heated. Although isotropic, Newtonian viscosity is a common feature of many coronal simulations, the proper form of viscosity in a highly magnetised plasma is anisotropic and strongly coupled to the local magnetic field. This thesis investigates the differences between isotropic viscosity and a novel family of models of anisotropic viscosity, the switching model, when applied to simulations of the kink and fluting instabilities in a coronal loop, a slowly stressed magnetic null point, and the Kelvin-Helmholtz instability in the fan plane of a null point. This switching model provides a method of resolving previously unresolved regions of isotropic viscosity near null points by essentially removing the perpendicular and drift terms from the Braginskii model of anisotropic viscosity and modifying the coefficients of the remaining terms. A number of potential switching models are presented, with one showing particular promise for use in numerical modelling of the solar corona, that based on the coefficient of the parallel term in the Braginskii model. The choice of viscosity model strongly affects the stability and evolution of the studied instabilities, and the heating generated in their development. The use of anisotropic viscosity generally diminishes viscous heating, enhances Ohmic heating, produces small scales in flow and current structures, results in more energetic instabilities and an overall increase in reconnection rate.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: solar physics, magnetohydrodynamics, viscosity, plasma physics, solar corona, anisotropic viscosity, plasma instability.
Subjects: Q Science > QA Mathematics
Q Science > QB Astronomy
Q Science > QC Physics
Colleges/Schools: College of Science and Engineering > School of Mathematics and Statistics > Mathematics
Supervisor's Name: MacTaggart, Dr. David
Date of Award: 2021
Depositing User: Dr James Quinn
Unique ID: glathesis:2021-82067
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 08 Apr 2021 12:11
Last Modified: 08 Apr 2021 12:16
Thesis DOI: 10.5525/gla.thesis.82067
URI: http://theses.gla.ac.uk/id/eprint/82067
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