The University of St Andrews

Research@StAndrews:FullText >
Mathematics & Statistics (School of) >
Applied Mathematics >
Applied Mathematics Theses >

Please use this identifier to cite or link to this item:
This item has been viewed 50 times in the last year. View Statistics

Files in This Item:

File Description SizeFormat
A.R. Yeates PhD thesis.pdf9.16 MBAdobe PDFView/Open
Accompanying software.zip36.84 MBZIPView/Open
Title: Development and application of a global magnetic field evolution model for the solar corona
Authors: Yeates, Anthony Robinson
Supervisors: Mackay, Duncan Hendry
Priest, Eric R.
Keywords: Sun
Solar filaments
Solar prominences
Coronal mass ejections
Magnetic field
Issue Date: 24-Jun-2009
Abstract: Magnetic fields are fundamental to the structure and dynamics of the Sun’s corona. Observations show them to be locally complex, with highly sheared and twisted fields visible in solar filaments/prominences. The free magnetic energy contained in such fields is the primary source of energy for coronal mass ejections, which are important—but still poorly understood drivers of space weather in the near-Earth environment. In this thesis, a new model is developed for the evolution of the large-scale magnetic field in the global solar corona. The model is based on observations of the radial magnetic field on the solar photosphere (visible surface). New active regions emerge, and their transport and dispersal by surface motions are simulated accurately with a surface flux transport model. The 3D coronal magnetic field is evolved in response to these photospheric motions using a magneto-frictional technique. The resulting sequence of nonlinear force-free equilibria traces the build-up of magnetic helicity and free energy over many months. The global model is applied to study two phenomena: filaments and coronal mass ejections. The magnetic field directions in a large sample of observed filaments are compared with a 6-month simulation. Depending on the twist of newly-emerging active regions, the correct chirality is simulated for up to 96% of filaments tested. On the basis of these simulations, an explanation for the observed hemispheric pattern of filament chirality is put forward, including why exceptions occur for filaments in certain locations. Twisted magnetic flux ropes develop in the simulations, often losing equilibrium and lifting off, removing helicity. The physical basis for such losses of equilibrium is demonstrated through 2D analytical models. In the 3D global simulations, the twist of emerging regions is a key parameter controlling the number of lift-offs, which may explain around a third of observed coronal mass ejections.
Type: Thesis
Publisher: University of St Andrews
Appears in Collections:Applied Mathematics Theses

This item is protected by original copyright

This item is licensed under a Creative Commons License
Creative Commons

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.


DSpace Software Copyright © 2002-2012  Duraspace - Feedback
For help contact: | Copyright for this page belongs to St Andrews University Library | Terms and Conditions (Cookies)