The continuous outward flow of ionized solar gas and a “frozen-in” remnant of the solar magnetic field through the solar system. This flow arises from strong outward pressure in the solar corona, becomes supersonic at a few solar radii (1 solar radius = 4.32 × 10⁵ mi or 6.96 × 10⁵ km) above the visible surface of the Sun (the photosphere), and attains speeds in the range 150–450 mi s⁻¹ (250–750 km s⁻¹) in interplanetary space. The solar wind is believed to remain supersonic out to a distance from the Sun of 50–100 astronomical units (AU), where it is slowed by interaction with the interstellar gas and magnetic field.