Wave Reflection in the Solar Atmosphere

Acoustic wave reflection in the solar atmosphere can provide insights into atmospheric heating by waves, chromospheric resonances, and the height of the plasma β=1 surface. We present strong evidence and validation of wave reflection in the lower chromosphere / upper photosphere region, through helioseismic analysis of multi-height Doppler data. This evidence is provided through our newly developed wave propagation model that incorporates downward traveling (reflected) plane waves in addition to upward traveling plane waves. The reflective region may be changing height with the magnetic field strength, hence suggesting that the β=1 region could act as a dynamic reflecting region. Furthermore, using the new model, we present estimates of the acoustic cutoff frequency, radiative damping time, sound speed, and the reflection coefficient in the solar atmosphere.