Topics: where the wind blows.

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.

Intriguing Items on Winds.

• In 2011, a massive dust storm, or "Haboob," struck Phoenix, Arizona. It was estimated that the dust cloud associated with the Haboob was 50 miles wide and 10,000 feet high. Haboobs occur in dry areas around the world and can leave up to a foot of sand in their wake.
  http://www.huffingtonpost.com/2011/07/06/phoenix-dust-storm-photos-video_n_891157.html
  https://en.wikipedia.org/wiki/Haboob
• Huge, planet-sized dust storms occur on Mars. They are most common during perihelion, when Mars is closest to the Sun, when the planet receives 40 percent more sunlight than during aphelion, creating pressure differences and wind storms.
  http://apod.nasa.gov/apod/ap030710.html
  http://www.nasa.gov/mission_pages/msl/multimedia/vasavada-4.html
• The solar wind carries about 1 million tons of material per second away from the Sun. Although it may seem like a lot, it is insignificant compared to the total mass of the Sun of about 2 million trillion trillion tons.
• Starting in May 2012 at 120 AU, the spacecraft Voyager 1 detected a sudden increase in cosmic rays, an apparent signature of approach to the heliopause, the region about 10 billion miles from Earth, where the pressure in the solar wind becomes equal to the pressure of the interstellar medium.

Back to the Wind page