Incompressible limit of ideal magnetohydrodynamics in a domain with boundaries

We study the incompressible limit of classical solutions to compressible ideal magneto-hydrodynamics in a domain with a flat boundary. The boundary condition is characteristic and the initial data is general. We first establish the uniform existence of classical solutions with respect to the Mach number. Then, we prove that the solutions converge to the solution of the incompressible MHD system. In particular, we obtain a stronger convergence result by using the dispersion of acoustic waves in the half space.