Non-radial Stellar Oscillations
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We use spherical coordinates r, ϑ, ϕ and describe the velocity of a mass element by a vector v having the components v r , v ϑ , v ϕ . For the radial pulsations treated in the foregoing sections, the velocity has only one non-vanishing component, v r , which depends only on r. This is so specialized a motion that one might wonder why a star should prefer to oscillate this way at all. In fact it is easier to imagine the occurrence of perturbations that are not spherically symmetric, for example those connected with turbulent motions or local temperature fluctuations. They can lead to non-radial oscillations, i.e. oscillatory motions having in general non-vanishing components v r , v ϑ , v ϕ , all of which can depend on r, ϑ, and ϕ. It is obvious that the treatment of the more general non-radial oscillations is much more involved than that of the radial case, but they certainly play a role in observed phenomena (see §40.4). We will limit ourselves to indicating a few properties of the simplest case: small (linear), adiabatic, poloidal-mode oscillations. For more details see, for instance, COX (1976, 1980), UNNO et al. (1979).
KeywordsGravity Wave Spherical Harmonic Oscillatory Motion Mass Element Radial Pulsation
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