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Stellar convection and dynamo theory

Miscellaneous:

Abstract

In considering the large scale stellar convection problem the outer layers of a star are modelled as two co-rotating plane layers coupled at a fluid/fluid interface. Heating from below causes only the upper fluid to convect, although this convection can penetrate into the lower fluid. Stability analysis is then used to find the most unstable mode of convection. With parameters appropriate to the Sun the most unstable mode is steady convection in thin cells (aspect ratio {approx equal} 0.2) filling the convection zone. There is negligible vertical motion in the lower fluid, but considerable thermal penetration, and a large jump in helicity at the interface, which has implications for dynamo theory. An {alpha}{omega} dynamo is investigated in isolation from the convection problem. Complexity is included by allowing both latitudinal and time dependence in the magnetic fields. The nonlinear dynamics of the resulting partial differential equations are analysed in considerable detail. On varying the main control parameter D (the dynamo number), many transitions of behaviour are found involving many forms of time dependence, but not chaos. Further, solutions which break equatorial symmetry are common and provide a theoretical explanation of solar observations which have this symmetry. Overall the behaviour was more  More>>
Authors:
Publication Date:
Oct 01, 1989
Product Type:
Miscellaneous
Reference Number:
AIX-22-078607; EDB-91-155406
Resource Relation:
Other Information: Thesis (Ph.D.)
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; STARS; CONVECTION; MAGNETIC FIELDS; MATHEMATICAL MODELS; ENERGY TRANSFER; HEAT TRANSFER; MASS TRANSFER; 640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources
OSTI ID:
5135194
Research Organizations:
Newcastle upon Tyne Univ. (United Kingdom)
Country of Origin:
United Kingdom
Language:
English
Availability:
Available from British Library Document Supply Centre, Boston Spa, Wetherby, West Yorks. LS23 7BQ. No. DX89704
Submitting Site:
GBN
Size:
Pages: (131 p)
Announcement Date:

Miscellaneous:

Citation Formats

Jennings, R L. Stellar convection and dynamo theory. United Kingdom: N. p., 1989. Web.
Jennings, R L. Stellar convection and dynamo theory. United Kingdom.
Jennings, R L. 1989. "Stellar convection and dynamo theory." United Kingdom.
@misc{etde_5135194,
title = {Stellar convection and dynamo theory}
author = {Jennings, R L}
abstractNote = {In considering the large scale stellar convection problem the outer layers of a star are modelled as two co-rotating plane layers coupled at a fluid/fluid interface. Heating from below causes only the upper fluid to convect, although this convection can penetrate into the lower fluid. Stability analysis is then used to find the most unstable mode of convection. With parameters appropriate to the Sun the most unstable mode is steady convection in thin cells (aspect ratio {approx equal} 0.2) filling the convection zone. There is negligible vertical motion in the lower fluid, but considerable thermal penetration, and a large jump in helicity at the interface, which has implications for dynamo theory. An {alpha}{omega} dynamo is investigated in isolation from the convection problem. Complexity is included by allowing both latitudinal and time dependence in the magnetic fields. The nonlinear dynamics of the resulting partial differential equations are analysed in considerable detail. On varying the main control parameter D (the dynamo number), many transitions of behaviour are found involving many forms of time dependence, but not chaos. Further, solutions which break equatorial symmetry are common and provide a theoretical explanation of solar observations which have this symmetry. Overall the behaviour was more complicated than expected. In particular, there were multiple stable solutions at fixed D, meaning that similar stars can have very different magnetic patterns, depending upon their history. (author).}
place = {United Kingdom}
year = {1989}
month = {Oct}
}