ACOUSTIC-WAVE PROPAGATION IN THE SOLAR ATMOSPHERE .1. LINEAR-RESPONSETO ADIABATIC WAVE EXCITATION

We study the response of various solar atmosphere models to excitation by adiabatic small amplitude acoustic waves. Both monochromatic waves and acoustic spectra are considered. We find that upon excitation, st rong resonance oscillations of a single frequency develop which are su perposed over the excitation signal. These resonances decay exponentia lly with time; the decay rate varies strongly with the temperature gra dient of the model. In realistic and positive gradient atmospheres the decay rate is much faster than in isothermal models, while in negativ e gradient models it is even slower. Independent of whether the atmosp here is excited by a pulse or by continuous wave action a similar deca y behaviour is found. The response to a stochastic wave spectrum is a series of uncorrelated transient events, each with the associated expo nential decay of the resonance.