THE suggestion of Biermann1 and Schwarzschild2, that the radially increasing temperature of the solar atmosphere is to be ascribed to propagation of non-thermal energy, such as acoustic waves, is now generally accepted. The effect of magnetic field, and the possibility that the energy-carrying waves are of a magnetohydrodynamic character rather than acoustic, has been considered seriously3. However, the fact that the density and temperature of the chromosphere are significantly affected by magnetic field only when the field attains the strength (∼ 50 gauss) which is found only in localized regions (plages) on the Sun's surface indicates that magnetic field is not of primary significance. Hence one may attempt to understand the energy propagation and its effects on the assumption that one can ignore the magnetic field and so consider only acoustic waves.