(shock wave of a magnetosphere through the surrounding medium)
A bow shock is a bow-shaped (arc-shaped) shock wave caused
by an object moving through a surrounding medium at higher
than the medium's speed of sound.
Unlike other shock waves, it is somewhat in front of the object
rather than touching it.
In some cases, a supersonic jet produces a bow shock in the
atmosphere.
A star or planet (e.g., Earth) can cause a bow shock
in the medium surrounding the star's or planet's magnetosphere.
The solar system was assumed to cause such a shock in the
interstellar medium but recent data suggests it does not, implying that the
relative speed of the solar system through the surrounding
medium is subsonic.