Bow Shock

In astrophysics, a bow shock is a bow shape volume in the space that forms the boundary between a magnetosphere and an ambient medium. Its name comes from the similar geometry that it shares with the waves made in front of a moving ship. For stars, this boundary is typically the edge of the astrosphere, where the stellar wind meets the interstellar medium. For a planetary magnetosphere, the bow shock is the boundary at which the speed of the stellar wind abruptly drops as a result of its approach to the magnetopause .The best-studied example of a bow shock is that occurring where the Sun's wind encounters Earth's magnetopause, although bow shocks occur around all magnetized planets, such as Jupiter or Saturn. Earth's bow shock is about 17 kilometres (11 mi) thick and located about 90,000 kilometres (56,000 mi) from the planet.