Abstract
SUMMARY Expressions are developed for the frequencies and amplitudes of spheroidal and toroidal modes, taking into account the rotational coupling between modes nSl - nTl+1. and nSl - nTl-1. Starting from quasi-degenerate perturbation theory, we derive coupled wave equations which clearly show the additional restoring force due to Coriolis coupling. We employ the subspace projection method to obtain asymptotic expressions for the perturbed amplitudes and frequencies, accurate to first order in coupling strength e and zeroth order in 1/l. The resulting expressions may be used to correct free oscillation amplitudes and frequencies in the fundamental Coriolis coupled band for the spheroidal-toroidal coupling. Data examples using preferentially aligned source-receiver paths verify the predicted patterns of amplitude and frequency perturbations.
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