# What is the solar wind? > The solar wind right now, live from spacecraft upstream of Earth: where it comes from, how long it takes to reach us, the bubble it blows, and what it does here. HTML: https://www.theuniversecounts.com/solar-system/space-weather/solar-wind Numbers as of 2026-10-31 03:44 UTC. Live ones keep changing on the HTML page. The solar wind is the Sun's outer atmosphere, blowing out into space in every direction. Right now it streams past Earth at 350 kilometres per second, measured by spacecraft upstream of us. At that speed it needs about 4.9 days to cross from the Sun to Earth. Sunlight makes the same trip in 8.3 minutes. Since you opened this page, the wind has travelled [counts up live on the page] kilometres. - Solar wind speed measured upstream of Earth: 350 km/s - Planetary K-index (Kp), latest 3-hour value: 3 - The Sun's X-ray brightness at Earth (GOES, 0.1–0.8 nm): B2.0 - Power flowing into the northern aurora (NOAA OVATION hemispheric power): 35,000,000,000 W ## The Sun's breath What is the solar wind? The Sun is a star, a ball of hot gas held together by its own gravity and lit by fusion in its core. Around it lies a thin, very hot outer atmosphere, the corona. The corona is so hot that the Sun's gravity can't hold all of it. Gas escapes from it all the time, faster than sound, and streams away in every direction. That stream is the solar wind. It is mostly protons and electrons, the pieces of hydrogen atoms, and it carries the Sun's magnetic field out with it. Right now it blows past Earth at 350 kilometres per second. ## Slow wind, fast wind Coronal holes The wind doesn't blow evenly. In the plane where the planets orbit, the usual state is a slow wind of about 400 kilometres per second, NOAA says. Faster streams pour out of coronal holes. These are dark patches in the corona where the Sun's magnetic field opens straight into space. Their wind runs at between 500 and 800 kilometres per second. The Sun's poles have large coronal holes that last, so fast wind fills the space far above and below the planets' orbits. The Sun turns once every 27 days as seen from Earth. So the wind spirals out like water from a turning garden sprinkler, and Earth passes through fast streams and slow ones in turn. When a fast stream catches up with slow wind ahead of it, the two pile up into a dense, strongly magnetic front. High-speed streams bring geomagnetic storms; slow wind brings calm space weather. ## A bubble around the planets The heliosphere The wind doesn't stop at Earth. It blows past every planet and blows a vast bubble around the Sun, called the heliosphere. So Earth lives inside the Sun's own atmosphere. Far out, the wind meets the thin gas between the stars and can push no further. That boundary is the heliopause. Voyager 1 crossed it on 25 August 2012, at 121.6 times Earth's distance from the Sun. Voyager 2 crossed in a different direction, at 119.0. Beyond it is interstellar space. Both spacecraft are still sending back what they find there. ## When the wind reaches us Earth's shield Earth has a shield against the wind: its magnetic field, made by molten iron churning in our planet's core. The wind presses this field in on the side facing the Sun and stretches it into a long tail on the night side. The bubble it makes is called the magnetosphere. It keeps most of the wind's particles away from us. Most of the time the wind just flows around it. When a fast stream or a cloud from a solar eruption arrives, and its magnetic field points the right way, energy pours in. The field shakes for hours or days. That is a geomagnetic storm, and it can light up the aurora far from the poles. Spacecraft at the L1 point, 1.5 million kilometres towards the Sun, measure the wind before it reaches us. That gives about an hour of warning. Comparisons are computed live on the HTML page. ## FAQ ### How fast is the solar wind? Right now 350 kilometres per second, past Earth. The usual slow wind runs at about 400, and fast streams from coronal holes at between 500 and 800 kilometres per second. ### How long does the solar wind take to reach Earth? At today's speed, about 4.9 days. Clouds from big solar eruptions can travel much faster. ### Can the solar wind hurt us? Not on the ground. Earth's magnetic field and atmosphere keep its particles away. When it is strong, it can cause geomagnetic storms that disturb satellites, GPS and power grids, and bring the aurora. ### Where does the solar wind end? At the heliopause, where it meets the gas between the stars. Voyager 1 crossed that boundary at 121.6 times Earth's distance from the Sun. ### Is the Sun losing mass to the solar wind? Yes, a little. Its light and its wind together take about 5.5 billion kilograms a second. The Sun is so massive that this barely matters over its life. ## Related - [What is the Sun doing right now?](https://www.theuniversecounts.com/solar-system/the-sun/what-is-the-sun-doing-now.md) - [Geomagnetic storms](https://www.theuniversecounts.com/solar-system/space-weather/geomagnetic-storms.md) - [The Sun](https://www.theuniversecounts.com/solar-system/the-sun.md) - [Voyager 1](https://www.theuniversecounts.com/solar-system/spacecraft/voyager-1.md) The wind that passes Earth tonight left the Sun days ago and is still on its way to the stars. What else have you lived inside without noticing? ## Sources - Concorde's cruising speed (Measured, with error): [British Airways: Celebrating Concorde](https://www.britishairways.com/content/en/information/about-ba/history-and-heritage/celebrating-concorde) - Diameter of a regulation football (size 5) (Measured, with error): [The IFAB: Laws of the Game, Law 2 – The Ball](https://www.theifab.com/laws/latest/the-ball/) - Distance from Earth to the L1 point, where the solar wind is measured (Measured): [NOAA SWPC: Aurora Tutorial](https://www.swpc.noaa.gov/content/aurora-tutorial) - Distance from the Sun to the heliopause, where the Voyagers crossed it (Estimated): [American Geophysical Union: Voyager Observations of the Heliospheric Interface (AGU Fall Meeting 2014 abstract)](https://studio.m-anage.com/agu/fm14/webprogram/Paper4456.html); [Nature Astronomy: Magnetic field and particle measurements made by Voyager 2 at and near the heliopause (Burlaga et al. 2019, Nature Astronomy)](https://doi.org/10.1038/s41550-019-0920-y); [NASA: Voyager Interstellar Mission](https://science.nasa.gov/mission/voyager/interstellar-mission/) - Earth's circumference at the equator (Measured): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Earth's diameter at the equator (Measured): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Equatorial diameter of Ceres (Measured): [Nature: A partially differentiated interior for (1) Ceres deduced from its gravity field and shape (Park et al., Nature 537, 515–517, 2016)](https://doi.org/10.1038/nature18955) - Great-circle distance between Copenhagen and London (Measured, with error): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Great-circle distance between London and Sydney (Measured, with error): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Mass the Sun loses each second, to its light and its wind together (Measured, with error): [NASA NSSDCA: Sun Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html); [Monthly Notices of the Royal Astronomical Society: The independency of stellar mass-loss rates on stellar X-ray luminosity and activity level based on solar X-ray flux and solar wind observations (Cohen 2011; arXiv:1107.2275)](https://doi.org/10.1111/j.1365-2966.2011.19428.x); [Astronomy & Astrophysics: Estimates of the change rate of solar mass and gravitational constant based on the dynamics of the Solar System (Pitjeva et al. 2021; arXiv:2201.09804)](https://doi.org/10.1051/0004-6361/202039893) - Official distance of a marathon (Measured): [World Athletics: Competition and Technical Rules, 2026 Edition](https://worldathletics.org/download/download?filename=acdec6c6-1261-4c7f-96d2-92f712707e99.pdf&urlslug=Competition+and+Technical+Rules+%E2%80%93+2026+Edition) - Planetary K-index (Kp), latest 3-hour value (Measured, with error): [NOAA SWPC: Planetary K-index](https://www.swpc.noaa.gov/products/planetary-k-index); [NOAA SWPC: NOAA Space Weather Scales](https://www.swpc.noaa.gov/noaa-scales-explanation) - Power flowing into the northern aurora (NOAA OVATION hemispheric power) (Measured, with error): [NOAA SWPC: Aurora - 30 Minute Forecast](https://www.swpc.noaa.gov/products/aurora-30-minute-forecast) - Solar wind speed measured upstream of Earth (Measured): [NOAA SWPC: Solar Wind Data and Display Changes (30 June 2026)](https://www.spaceweather.gov/news/solar-wind-data-and-display-changes); [NOAA SWPC: SWPC home-page summary bar script (shows this file as "Solar Wind Speed ... km/sec")](https://www.swpc.noaa.gov/modules/custom/swpc_summary/swpc_summary.js); [The Astrophysical Journal: Extremely Slow (Vsw < 300 km/s) Solar Winds (ESSWs) at 1 au: Causes of Extreme Geomagnetic Quiet at Earth (Tsurutani & Hajra 2022, ApJ 936, 155)](https://doi.org/10.3847/1538-4357/ac7444); [Journal of Geophysical Research: Extremely high speed solar wind: 29-30 October 2003 (Skoug et al. 2004, JGR 109, A09102)](https://doi.org/10.1029/2004JA010494); [Space Weather (AGU): On the Little-Known Consequences of the 4 August 1972 Ultra-Fast Coronal Mass Ejecta (Knipp et al. 2018, Space Weather 16)](https://doi.org/10.1029/2018SW002024) - Speed of light in a vacuum (Measured): [BIPM: SI defining constants](https://www.bipm.org/en/measurement-units/si-defining-constants) - Speed of the fast solar wind from coronal holes (Measured): [NOAA Space Weather Prediction Center: Solar Wind](https://www.swpc.noaa.gov/phenomena/solar-wind) - The International Space Station's orbital speed (Measured): [NASA: Station Facts](https://www.nasa.gov/international-space-station/space-station-facts-and-figures/) - The Moon's average distance from Earth (Measured): [NASA: Moon Facts](https://science.nasa.gov/moon/facts/) - The Sun's distance from Earth (Measured): [NASA NSSDCA: Sun Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html) - The Sun's X-ray brightness at Earth (GOES, 0.1–0.8 nm) (Measured): [NOAA SWPC: Solar Flares (Radio Blackouts)](https://www.swpc.noaa.gov/phenomena/solar-flares-radio-blackouts) - Time since Voyager 1 went interstellar (Measured): [NASA: Voyager Interstellar Mission](https://science.nasa.gov/mission/voyager/interstellar-mission/); [American Geophysical Union: Voyager Observations of the Heliospheric Interface (AGU Fall Meeting 2014 abstract)](https://studio.m-anage.com/agu/fm14/webprogram/Paper4456.html) - Time the Sun takes to turn once as seen from Earth (synodic, Carrington rotation) (Measured): [Wilcox Solar Observatory, Stanford University: Solar-Terrestrial Coordinate Systems](http://wso.stanford.edu/words/Coordinates.html) - Typical muzzle velocity of a rifle bullet (Estimated): [Headquarters, Department of the Army: FM 3-22.9 Rifle Marksmanship: M16A1, M16A2/3, M16A4, and M4 Carbine (April 2003)](https://www.bits.de/NRANEU/others/amd-us-archive/FM3-22.9%2803%29.pdf) - Typical speed of the slow solar wind, in the planets' plane (Measured): [NOAA Space Weather Prediction Center: Solar Wind](https://www.swpc.noaa.gov/phenomena/solar-wind) - Voyager 1's distance from the Sun when it crossed the heliopause (Measured): [American Geophysical Union: Voyager Observations of the Heliospheric Interface (AGU Fall Meeting 2014 abstract)](https://studio.m-anage.com/agu/fm14/webprogram/Paper4456.html); [NASA: Voyager Interstellar Mission](https://science.nasa.gov/mission/voyager/interstellar-mission/) - Voyager 2's distance from the Sun when it crossed the heliopause (Measured): [Nature Astronomy: Magnetic field and particle measurements made by Voyager 2 at and near the heliopause (Burlaga et al. 2019, Nature Astronomy)](https://doi.org/10.1038/s41550-019-0920-y); [Nature Astronomy: Cosmic ray measurements from Voyager 2 as it crossed into interstellar space (Stone et al. 2019, Nature Astronomy)](https://doi.org/10.1038/s41550-019-0928-3); [NASA JPL: Voyager 2 Illuminates Boundary of Interstellar Space](https://www.jpl.nasa.gov/news/voyager-2-illuminates-boundary-of-interstellar-space)