Wind, the flow of gases on a large scale caused by differences in pressure, occurs on Earth, planets, in interplanetary space, around starts, and in galaxies. Wind on Earth can exist for a few minutes, as in a thunderstorm, to local breezes generated by
heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth.
Particles are transported by winds through suspension, saltation (skipping or bouncing) and creeping (rolling or sliding) along the ground. Small particles may be held in Earth's atmosphere in suspension. Typical winds near Earth's surface suspend particles less than 0.2 millimeters (0.08 inches) in diameter and scatter them aloft as dust, smog, or haze, or sparks. Embers from wildfires have carried embers as far as 10 kilometers (6 miles) from the fire front, to start new fires.
A wind can occur wherever a difference in pressure between two locations is not balanced by some other force such as gravity. Winds have been observed on other planets, in interplanetary space as the solar wind, around stars (stellar winds), and in galaxies, where they can produce dramatic effects through their ability to move particles from one place to another.
The heating of the Sun's upper atmosphere produces the solar wind, a stream of charged particles which flows away from the Sun at speeds of millions of miles per hour. The impact of the solar wind on Earth's upper atmosphere can produce geomagnetic storms that generate auroras, and can knock out power grids. The solar wind also creates the heliosphere, a vast bubble in the interstellar medium that surrounds the Solar System.
On a larger scale, some unusual galaxies undergo bursts of star formation, often as a result of collisions between galaxies. The most massive of the stars race through their evolution and explode as supernovas. If the rate of supernovas are high enough, the combined effects of many supernova shock waves drives a galactic-scale wind that blows gas off the galaxy. A prime example is the galaxy M82. Galactic winds such as the one in M82 are rare today, but they were common billions of years ago when collisions between galaxies were more frequent.
Chandra showed that the Sculptor Wall, a collection of gas and galaxies that stretches across tens of millions of light years, contains a vast reservoir of gas enriched in oxygen from galactic winds. The Sculptor Wall is thought to be part of an enormous web of hot, diffuse gas containing as much as half of all the ordinary matter in the Universe.
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"Here, There, & Everywhere" (HTE) is supported by the National Aeronautics and Space Administration under grant NNX11AH28G issued through the Science Mission Directorate.