Linear and nonlinear properties of waves excited by the mirror instability in high beta, low anisotropy (&bgr;⊥>&bgr;∥≥1) plasmas characteristic of the magnetosheath are investigated using linear theory and one-dimensional hybrid simulations. The mechanisms for wave growth and saturation at low amplitudes are discussed. A new method is considered for generating the large amplitude mirror waves observed in the magnetosheath based on external compression of magnetic flux tubes. Simulations in which the anisotropy is maintained by recycling the ions shows this process can inhibit the growth of ion cyclotron waves and enhances the growth of mirror waves. ¿ American Geophysical Union 1992