Some properties of the formation of fast magnetosonic shocks

•Magnetosonic waves may evolve into shock waves.•The problem is analyzed in detail for vertical magnetic fields and plane flows.•The essential parameter is the curvature of wavefronts.•The method may be extended to two-species and reactive plasmas.

Nonlinear waves advancing into equilibrium states may become shocks. This possibility depends on the equilibrium quantities plus the velocity and shape of the wavefronts. The equation describing this phenomenon is described for the case of the fast magnetosonic waves, and the particular case of plane flow with vertical magnetic field is analyzed in detail. It is also shown that in two-species MHD, both collisions between species and their chemical reactivity tend to delay or prevent the formation of shocks.