Does a Non-Magnetic Solar Chromosphere Exist?
  Enhanced chromospheric emission which corresponds to an outwardly increasing semiempirical temperature structure can be produced by wave motion without any increase in the mean gas temperture. Hence, the sun may not have a classical chromosphere in magnetic field free internetwork regions. Other significant differences between the properties of dynamic and static atmospheres should be considered when analyzing chromospheric observations. 
Mats Carlsson and Robert F. Stein