Bow shock

A curved shock wave forms upstream of an obstacle when a plasma flow approaches faster than pressure disturbances can propagate. It abruptly slows, heats, and redirects the plasma.

Magnetohydrodynamic shock: A discontinuity in a conducting fluid that sharply changes its flow and magnetic-field properties. A bow shock is a curved, spatially extended example of this plasma-flow discontinuity.
Earth's bow shock: The curved shock upstream of Earth’s magnetosphere, where the solar wind first undergoes abrupt deceleration and heating. It is the best-studied planetary example and the upstream boundary of Earth's magnetosheath.
Sydney Chapman: A British geophysicist whose work shaped the early theory of Earth's ionosphere and magnetosphere. His theoretical work helped establish the possibility of a shock ahead of Earth's magnetic obstacle.
Space weather: Conditions in space driven by solar activity and solar-wind interactions that affect planets and technology. Earth’s bow shock changes the solar wind before it reaches the magnetosphere and can influence space-weather conditions.
Magnetopause: The boundary separating a planet’s magnetosphere from the surrounding solar wind. It lies downstream of Earth’s bow shock, with the magnetosheath between the two boundaries.
Magnetosonic speed: The speed at which combined magnetic and pressure disturbances propagate through a plasma. The upstream flow must exceed the relevant wave speed for a bow shock to form.
Jupiter's bow shock: The shock formed as the solar wind encounters Jupiter’s large magnetosphere. Its variable distance from Jupiter shows how a planet’s shock responds to changing solar-wind conditions.
Luna 1: The first spacecraft to reach the vicinity of the Moon, launched by the Soviet Union in 1959. Its measurements provided early evidence for a shock associated with Earth’s interaction with the solar wind.
Diffusive shock acceleration: A process in which charged particles gain energy by repeatedly crossing a shock front. Bow shocks can accelerate particles that cross between the upstream flow and shocked plasma.
Bow wave: A compression wave that forms ahead of an obstacle moving through a medium without a shock discontinuity. A sub-fast flow can produce a bow wave, whereas a sufficiently fast flow produces a bow shock.

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