ABSORPTION OF WAVES IN ACCRETION DISKS .1. RESONANCE AT THE RADIUS WHERE THE WAVE FREQUENCY MATCHES THE VERTICAL BRUNT-VAISALA FREQUENCY

The propagation properties of internal gravity waves in a rotating tor us are considered. The oscillations are assumed to be axisymmetric and adiabatic. In the short-wavelength limit in the vertical direction, t he gravity waves whose frequency is omega are confined in the region i n which [omega - N(r)][omega - kappa(r)] < 0 holds, where N and kappa are the Brunt-Vaisala frequency for vertical displacement and the epic yclic frequency, respectively, and r is the radial coordinate. We find that the gravity waves are resonantly absorbed to heat the plasma at the radius where omega equals N(r). This radius is probably located in the innermost region of the torus, where most X-rays are emitted. Som e implications of this result, with respect to quasi-periodic oscillat ions obserbed from low-mass X-ray binaries, are briefly discussed.