Solar Physics Division Meeting 2000, June 19-22
Session 1. Helioseismology, Magnetic Fields, Chromosphere and Transition Region
Display, Chair: C. U. Keller, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[1.30] Acoustic Waves in a Three-Dimensional Stratified Atmosphere

W. Kalkofen (Harvard-Smithsonian CfA), S. Massaglia (Dipartimento di Fisica Generale dell'Università, Torino), G. Bodo, P. Rossi (Osservatorio Astronomico di Torino)

We investigate the propagation of acoustic waves in a three-dimensional, nonmagnetic, isothermal atmosphere stratified in plane-parallel layers in a study of oscillations in chromospheric calcium bright points. We present analytic results for the linear and numerical results for the nonlinear evolution of a disturbance. An impulsively excited acoustic disturbance emanates from a point source and propagates outward as a spherical acoustic wave, amplifying exponentially in the upward direction. A significant wave amplitude is found only in a relatively narrow cone about the vertical. The amplitude of the wave and the opening angle of the cone decrease with time. Because of the lateral spread of the upward-propagating energy, the decay is faster in 2D and 3D simulations than in 1D. We discuss observational consequences of this scenario, some of which are not anticipated from 1D calculations.

We acknowledge support from NASA, NSF and the Ministero per l'Università e la Ricerca Scientifica e Tecnologica.

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