Solar Wind Speed (typical)
| Value | 400,000 m/s |
| Status | Conventional / typical value |
| Source | NASA/ESA in-situ measurements (ACE, Wind, Parker Solar Probe); representative value |
| Categories | Astronomical |
| millimeter per year | 1.2623040e+16 mm/yr |
| millimeter per day | 34,560,000,000,000 mm/day |
| millimeter per hour | 1,440,000,000,000 mm/h |
| inch per day | 1,360,629,900,000 in/day |
| foot per day | 113,385,830,000 ft/d |
| inch per hour | 56,692,913,000 in/h |
| meter per day | 34,560,000,000 m/d |
| millimeter per minute | 24,000,000,000 mm/min |
| meter per hour | 1,440,000,000 m/h |
| inch per minute | 944,881,890 in/min |
| millimeter per second | 400,000,000 mm/s |
| foot per minute | 78,740,157 ft/min |
| centimeter per second | 40,000,000 cm/s |
| meter per minute | 24,000,000 m/min |
| inch per second | 15,748,031 in/s |
| kilometer per hour | 1,440,000 km/h |
| foot per second | 1,312,336 ft/s |
| mile per hour | 894,774.52 mph |
| knot | 777,537.8 kn |
| meter per second | 400,000 m/s |
| mach (sea level) | 1,175.4542 Ma |
| kilometer per second | 400 km/s |
| speed of light | 0.0013342564 c |
Learning zone
Eugene Parker argued in 1958 that the Sun's million-kelvin corona cannot be held down by gravity and must be flowing outward continuously — a paper two referees rejected before Chandrasekhar overruled them. Mariner 2 confirmed the supersonic wind on its way to Venus in 1962. This entry is a representative value, not a constant: the slow wind from the streamer belt arrives near 400 km/s, coronal-hole fast streams reach 700–800 km/s, and coronal mass ejections have exceeded 2000 km/s.
At 400 km/s the plasma takes about four days to cross the 1 au to Earth, which is the practical warning time for space weather. The wind carves the heliosphere out of the interstellar medium; Voyager 1 crossed its outer boundary, the heliopause, at 121 au in 2012.