Slow magneto-acoustic waves are often observed in polar plumes and active region fan loops. The observed periodicities of these waves are in the range of 1- 40 minutes. Mainly, the ratio of damping time to the oscillation period is less than 2 (equal to the ratio damping length to the wave length), which corresponds to the strong damping regime. In general, slow magneto-acoustic waves can be da...

Porous materials have good acoustic damping characteristics over a wide frequency range. As for sound waves, many small-scale pores in the coating materials can convert underwater-coating to rough surfaces. The main property of porous absorbents is their resistance against incident sound wave that leads to damping effect. From a physical point of view, damping occurs due to friction between flu...