Book contents
- Frontmatter
- Contents
- Preface
- 1 The basic fluid equations
- 2 Compressible media
- 3 Spherically symmetric flows
- 4 Stellar models and stellar oscillations
- 5 Stellar oscillations – waves in stratified media
- 6 Damping and excitation of stellar oscillations
- 7 Magnetic instability in a static atmosphere
- 8 Thermal instabilities
- 9 Gravitational instability
- 10 Linear shear flows
- 11 Rotating flows
- 12 Circular shear flow
- 13 Modes in rotating stars
- 14 Cylindrical shear flow-non-axisymmetric instability
- References
- Index
4 - Stellar models and stellar oscillations
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- 1 The basic fluid equations
- 2 Compressible media
- 3 Spherically symmetric flows
- 4 Stellar models and stellar oscillations
- 5 Stellar oscillations – waves in stratified media
- 6 Damping and excitation of stellar oscillations
- 7 Magnetic instability in a static atmosphere
- 8 Thermal instabilities
- 9 Gravitational instability
- 10 Linear shear flows
- 11 Rotating flows
- 12 Circular shear flow
- 13 Modes in rotating stars
- 14 Cylindrical shear flow-non-axisymmetric instability
- References
- Index
Summary
In the next few chapters we consider what happens if we perturb a stationary fluid configuration. The unperturbed configuration we have in mind is a body of fluid at rest in a stationary gravitational potential well. This potential might result from the self-gravity of the fluid itself, as for a star, or it might be produced by some external agency. An example of the latter case is the potential well produced by the dark matter component of a cluster of galaxies. The intracluster medium sits in this potential, without significantly contributing to it.
Studying perturbations in this way is important for a number of reasons. We can often use a linear analysis, and thus make things mathematically tractable. Working out when perturbations grow or not often provides us with a good idea of how a system will react, even to finite (non-infinitesimal) perturbations. In particular, we may be able to decide if the system is likely to react with drastic changes (instability), or settle down again to a state rather like its original one (stability). A system's reaction to perturbations also tells us a lot about its structure. Just as geophysicists learn about the Earth's interior by studying how it reacts to perturbations such as earthquakes, astronomers can use a similar technique (asteroseismology) to study the interior of stars.
Models of stars
To be specific we shall mainly consider perturbations to models of stars, although the results we find are generally applicable.
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- Chapter
- Information
- Astrophysical Flows , pp. 60 - 77Publisher: Cambridge University PressPrint publication year: 2007