The temperature structure of the chromosphere is interesting. At a height of approximately 500km there is a temperature minimum around 4200K. Moving to a height of 2300km the temperature increases to approximately 10000K. After corona reaches these temperature values, it starts to cool down farther we go from the Sun.

This phenomenon can only be explained by heating of the solar atmosphere. During the last century, oscillations were suggested as one of the source of heating in the atmosphere, second suggested mechanism was magnetic reconnection.

 

From the theoretical standpoint the high frequency oscillations with periods from 6mHz to 100mHz are assumed to be the main carrier of the required energy for the heating of the upper layers of the atmosphere. and the heating should balance the radiative loss (Kalkofen 2001). However, the observational works (Fossum and Carlsson 2007, Andic 2007) could not find enough energy to confirm this standpoint.  At the moment Wedemeyer-Bohn and his team works at the multidimensional model which might explain is there significant contribution of the acoustic waves to the energy supply.  However this question is not yet fully resolved.