Internal Ray Paths
Three kinds of waves are looked for by helioseismologists: acoustic waves, for which pressure is the restoring force (these waves generate p modes), gravity waves for which buoyancy is the restoring force (these waves generate g modes), and surface gravity waves (these waves generate f modes). [Harvey, 1995, pp. 33] Helioseismologists use both standing wave patterns and propagating waves in their research.
The above Figure shows a diagram of ray paths of different acoustic (pressure) waves inside of the Sun. A resonant solar cavity is a region of the solar interior in which the acoustic wave is confined by the laws of propagation. [Noyes, 1990,pp. 22] The acoustic waves are bounded on top by a huge drop in density near the surface. And on the bottom of the cavity, the ray paths are bent as the sound speed increases with depth. Why? As the speed of sound increases with temperature, which in the Sun, increases with depth, the wave's inner edge travels faster than its outer edge, causing it to bend towards the surface. The angle at which the wave reflects determines how far it will penetrate: The shallower the angle, the shallower the penetration.
Last Modified by ALG on September 14, 1997.