This paper establishes a set of static magnetohydrodynamics equations in which a differential rotation of the magnetosphere and a wavy magnetodisc structure are considered. Solutions are obtained that include magnetic field, pressure, density, and temperature. By using the theoretical formulas of the magnetic field and pressure, we calculate the thickness of the plasma sheet. The main results are as follows. First, the thickness of the plasma sheet is determined by the thermal energy and the rotational energy of the plasma, and moreover, it increases with increasing thermal energy (temperature) and decreases with increasing rotational energy. Secondly, the thickness of the plasma sheet is different under adiabatic and isothermal conditions. Thirdly, in the isothermal case when &bgr;0>0.86 (&bgr;0 = &OHgr;J2L0/2RT0), the thickness initially increases with increasing radial distance, reaches a maximum, and then decreases; for &bgr;0<0.86 in the isothermal case and for all &bgr;0 in the adiabatic case, the thickness decreases monotonically with increasing radial distance.