The shock wave in front of an object moving through a gas or liquid medium. The most familiar solar-system example is the shock-wave front between the magnetic field of a planet and the solar wind. It is the outer boundary of a planetary magnetosphere, where the solar wind is slowed from supersonic to subsonic velocities. It forms upwind of the magnetopause (the boundary where the planet is shielded from the solar wind).
Subjects: Astronomy and Astrophysics — Earth Sciences and Geography.