The compressibility of the earth's core and the anti-dynamo theorems
Thesis (M.Sc.)--Memorial University of Newfoundland, 1979. Physics Bibliography: leaves 71-73. Anti-dynamo theorems are proofs that certain combinations of magnetic and velocity fields cannot produce the dynamo action needed to sustain the magnetic field. They can be divided into two classes. One cl...
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ftmemorialunivdc:oai:collections.mun.ca:theses2/43137 2023-05-15T17:23:30+02:00 The compressibility of the earth's core and the anti-dynamo theorems Todoeschuck, John Peter, 1955- Memorial University of Newfoundland. Dept. of Physics 1979 73 leaves : ill. Image/jpeg; Application/pdf http://collections.mun.ca/cdm/ref/collection/theses2/id/43137 Eng eng Electronic Theses and Dissertations (9.21 MB) -- http://collections.mun.ca/PDFs/theses/Todoeschuck_JohnPeter.pdf 75032246 http://collections.mun.ca/cdm/ref/collection/theses2/id/43137 The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries Magnetohydrodynamics Cosmic magnetic fields Earth--Core Text Electronic thesis or dissertation 1979 ftmemorialunivdc 2015-08-06T19:16:35Z Thesis (M.Sc.)--Memorial University of Newfoundland, 1979. Physics Bibliography: leaves 71-73. Anti-dynamo theorems are proofs that certain combinations of magnetic and velocity fields cannot produce the dynamo action needed to sustain the magnetic field. They can be divided into two classes. One class applies only to magnetic fields that are constant in time. The second is concerned with the more general case of magnetic fields that are allowed to vary in time. -- The previously accepted proofs of this second class are not generally valid in a compressible fluid. An anti-dynamo theorem can be applied in a particular case only if the parameter Rmc is much less than one. This parameter is given by - Rmc = CRm -- where Rm is the magnetic Reynolds number or the ratio of the importance of transport processes to ohmic diffusion and C is the Smylie-Rochester compressibility number which gives the fractional compression of material. -- For large scale processes involving substantial radial motion in the core of the Earth C is about 0.2 while Rm is about 200. Thus an anti-dynamo theorem for time-dependent axisymmetric velocity and magnetic fields does not apply to the core of the Earth. Another theorem for non-radial velocity fields is probably applicable as the density difference on any surface of constant radius in the core is not likely to be large. A third theorem on two-dimensional fields is hard to apply to the Earth because the system considered in the theorem is of infinite extent along one axis. -- The theorems of the first class are not affected by the introduction of compressibility. Thesis Newfoundland studies University of Newfoundland Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
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Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
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ftmemorialunivdc |
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English |
topic |
Magnetohydrodynamics Cosmic magnetic fields Earth--Core |
spellingShingle |
Magnetohydrodynamics Cosmic magnetic fields Earth--Core Todoeschuck, John Peter, 1955- The compressibility of the earth's core and the anti-dynamo theorems |
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Magnetohydrodynamics Cosmic magnetic fields Earth--Core |
description |
Thesis (M.Sc.)--Memorial University of Newfoundland, 1979. Physics Bibliography: leaves 71-73. Anti-dynamo theorems are proofs that certain combinations of magnetic and velocity fields cannot produce the dynamo action needed to sustain the magnetic field. They can be divided into two classes. One class applies only to magnetic fields that are constant in time. The second is concerned with the more general case of magnetic fields that are allowed to vary in time. -- The previously accepted proofs of this second class are not generally valid in a compressible fluid. An anti-dynamo theorem can be applied in a particular case only if the parameter Rmc is much less than one. This parameter is given by - Rmc = CRm -- where Rm is the magnetic Reynolds number or the ratio of the importance of transport processes to ohmic diffusion and C is the Smylie-Rochester compressibility number which gives the fractional compression of material. -- For large scale processes involving substantial radial motion in the core of the Earth C is about 0.2 while Rm is about 200. Thus an anti-dynamo theorem for time-dependent axisymmetric velocity and magnetic fields does not apply to the core of the Earth. Another theorem for non-radial velocity fields is probably applicable as the density difference on any surface of constant radius in the core is not likely to be large. A third theorem on two-dimensional fields is hard to apply to the Earth because the system considered in the theorem is of infinite extent along one axis. -- The theorems of the first class are not affected by the introduction of compressibility. |
author2 |
Memorial University of Newfoundland. Dept. of Physics |
format |
Thesis |
author |
Todoeschuck, John Peter, 1955- |
author_facet |
Todoeschuck, John Peter, 1955- |
author_sort |
Todoeschuck, John Peter, 1955- |
title |
The compressibility of the earth's core and the anti-dynamo theorems |
title_short |
The compressibility of the earth's core and the anti-dynamo theorems |
title_full |
The compressibility of the earth's core and the anti-dynamo theorems |
title_fullStr |
The compressibility of the earth's core and the anti-dynamo theorems |
title_full_unstemmed |
The compressibility of the earth's core and the anti-dynamo theorems |
title_sort |
compressibility of the earth's core and the anti-dynamo theorems |
publishDate |
1979 |
url |
http://collections.mun.ca/cdm/ref/collection/theses2/id/43137 |
genre |
Newfoundland studies University of Newfoundland |
genre_facet |
Newfoundland studies University of Newfoundland |
op_source |
Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries |
op_relation |
Electronic Theses and Dissertations (9.21 MB) -- http://collections.mun.ca/PDFs/theses/Todoeschuck_JohnPeter.pdf 75032246 http://collections.mun.ca/cdm/ref/collection/theses2/id/43137 |
op_rights |
The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. |
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1766112813652115456 |