Dependence of the canopy height of solar magnetic flux tubes on its definition

By analyzing a canopy tube described by Athay, we point out the possibility that the different canopy heights given by different authors are caused by different definitions of canopy heights. For the same canopy tube, those heights where the magnetic field has horizontal components, where neighboring magnetic tubes meet each other and where the magnetic field becomes uniform or vertical range from near the solar photosphere to the solar corona.