Generation and Propagation of Waves in the Solar Atmosphere.

We have studied the propagation of compressible waves of small amplitude from a fluctuating point source in an isothomal atmosphere. Using Lighthill's method of stationary phase, we have computed surfaces of constant phase, group velocities, and amplitude distributions in the radiation field. The existence of a trapped band of frequencies at the resonance frequency of the atmosphere suggests a mechanism for the observed oscillations. The trapping of waves in an atmosphere of variable temperature has also been treated and discussed in relation to the observed oscillations. Certain qualitative features of the observations seem to be explainable in terms of these results. The waves and oscillations may be generated by turbulence resulting from shear instabilities in the large horizontal flows (supergranulation). This is one possible explanation of the observed temperature-velocity correlation. Analogies to experimental convection are noted. This work was supported by the Air Force Office of Scientific Research under Contract No. AF 49(638)1065.