A Quasi-One-Dimensional Model for a Solar Flux Tube

We develop the quasi-one-dimensional flux tube model with magnetohydrodynamical equations. In order to know whether the magnetic field can maintain their similar structure from photosphere to chromosphere, we suppose that the flux tube is thin in radius relative to the length, the quantities in the cross section is averaged. The radii of the flux tube and the magnetic field are numerically simulated. One of the important results shows that the fluxtube does not expand quickly as existed model when it is out of the photosphere with high velocity. This is consistent with observations of the magnetic field in photosphere and chromosphere.