The Alfv¿n shock structure is obtained by a two-fluid simulation code including dissipations due to resistivity, viscosity and heat conductivity. The hodogram of the tangential magnetic field component of the simulated Alfv¿n shock is S-shaped with a 180¿ angular rotation. This is the first simulation result to show the S-shaped hodogram associated with Alfv¿n shocks. The S-shaped hodograms have been observed at the magnetopause [Berchem and Russell, 1982>. On the basis of this result, we propose that the magnetopause is an Alfv¿n shock where and when the hodogram is S-shaped and rotates 180¿. The upstream portion of the hodogram is always right-hand polarized; the downstream portion is always left-handed. The thickness of the Alfv¿n shock transition layer is about a few ion inertial lengths, which tends to increase with decreasing shock normal angle &thgr;bn. For &thgr;bn=80¿, the thickness is estimated to be about 5 c/&ohgr;pi. ¿ American Geophysical Union 1989