The phenomenon recorded by a space probe that leaves the solar wind and flies into a planet's magnetosphere. This happens during the end of the vehicle's far encounter phase involving the planet or at the beginning of the near encounter phase. The bow shock crossing is identified from data collected by a magnetometer, a plasma instrument, and a plasma-wave instrument. When the solar-wind magnetosphere boundary swings back and forth (often over millions of kilometres), the spacecraft will encounter many bow shock crossings.