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M. Roth, M. Stix (Kiepenheuer-Institut für Sonnenphysik)
Time-dependent and stationary velocity fields in the solar convection zone lead to coupling of solar oscillations, which result in splittings of the degenerate p-mode frequencies into multiplets. These splittings are antisymmetric in the case of differential rotation, i.e., pure toroidal fields, and asymmetric in the case of overturning convection cells, i.e., poloidal fields. The reason for these effects are intermixtures of the p-mode eigenfunctions expressed in a linear expansion of the coupling unperturbed eigenstates.
In analogy to a perturbed quantum-mechanical system of discrete eigenstates, where the squares of the expansion coefficients are related to the transition probability between the states, we use time-dependent perturbation theory to derive an expression for the expansion coefficients of the p-mode coupling. There the square of the coefficients is regarded as energy distribution of the perturbed sytem.
We conclude that a time-dependent velocity field has not only effects on the p-mode splitting, but has also influence on the lifetime and therefore the linewidth of the power spectra.
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