Recent obsevations indicate that a region of enhanced plasma pressure and decreased magnetic field intensity frequently occurs in front of the plasma depletion layer at the dayside magnetopause [Song et al., 1990>. This inverse relationship is characteristic of a slow-mode wave. We have simulated this phenomenon with a two-dimensional incompressible MHD simulation code. When a normal component of the interplanetary magnetic field is present (Bx≠0), the total magnetic field intensity tends to decrease in front of the depletion layer due to the bending of the magnetic field lines, and the plasma pressure is enhanced in this region. On the other hand, when Bx=0, this low-mode structure is not present in the simulation and only the plasma depletion layer is observed. ¿ American Geophysical Union 1991