Chorley, N. (2011) Spatial and temporal analysis of sunspot oscillations. PhD thesis, University of Warwick.

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Abstract

Sunspots are the most conspicuous feature seen on the solar photosphere and are
manifestations of the solar magnetic field. Their study, then, may provide us with a
greater understanding of the dynamo mechanism thought to be responsible for the
generation of this field.
In this thesis, the oscillations of sunspots are studied by making use of observational
data from two instruments: the Nobeyama Radioheliograph (NoRH) and
the Solar Optical Telescope (SOT) on board the Hinode spacecraft.
First, a study of long period oscillations was undertaken in which two long
period peaks (P > 10 min) were identified in the power spectra of time series
generated from sets of images of 3 sunspots observed with NoRH. In addition, by
using the techniques of period, power, correlation and lag mapping, it was found
that the power in each of these peaks was concentrated over the umbral regions
and that there were two regions of approximately equal size oscillating in anti-phase
with each other. It was suggested that these properties could be signatures of a
"shallow" sunspot.
A follow-up study was then performed, in which the lifetimes of the long
period oscillations were investigated over a period of 9 days. These oscillations were
seen to dominate the spectra during this interval and the periods and amplitudes
were stable during that time. A simple model of a damped, driven simple harmonic
oscillator (in which the driving term was nonlinear) was proposed to explain the
generation and support of the oscillations.
Finally, a study of the spatial properties of the 3 minute oscillations was
performed by applying the mapping techniques mentioned above to Hinode/SOT
data. The distributions of power and lag of maximum correlation coefficient were
found to be non-uniform over the sunspots under study and this may be indicative
of inhomogeneities of the physical quantities in the structures.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QB Astronomy
Library of Congress Subject Headings (LCSH):	Sunspots, Solar oscillations, Solar magnetic fields
Official Date:	June 2011
Dates:	Date Event June 2011 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Hnat, B.
Extent:	xv, 124 leaves : ill., charts
Language:	eng

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