Bow shock
In astrophysics, a bow shock triggers when the magnetosphere of an astrophysical object interacts with the nearby flowing ambient plasma such as the solar wind. For Earth and other magnetized planets, it is the border at which the speed of the stellar wind suddenly drops as a result of its approach to the magnetopause. For stars, this border is usually the edge of the astrosphere, where the stellar wind meets the interstellar medium.