Auroras provide visual entertainment in regions close to the poles, and observers are eager for the auroras to appear. On the other hand, geomagnetic storms threaten GPS units and satellites. Both are caused by the same phenomenon, called the solar wind.
Identification
The solar wind is a stream of superheated particles that have escaped from the sun's corona and magnetic field. The atmosphere above the sun's surface becomes extremely hot. Why the atmosphere becomes so hot instead of cooling down is unknown, but this heat makes the particles in the atmosphere start to move at high speed. The magnetic field of the sun is weakened at the poles, and the wind escapes through there. The resulting high-speed cloud expands out into space.
History
The solar wind was first noticed in the 1600s through comets. Their tails point away from the sun at all times. In the mid 20th century, German astronomers Cuno Hoffmeister and Ludvig Biermann both noted, separately, that some sort of particle stream might be affecting comet tails. Finally, in 1958, Eugene Parker at the University of Chicago realized the particles were coming from the sun's corona and were heated to an extreme degree.
Heliopause
The solar wind is powerful enough to push its way past several planets, but it does reach a point where it slows down and becomes ineffective when faced with other planets' magnetic fields. This area is called the heliopause. The point at which the wind slows dramatically is known specifically as the heliospheric termination shock. However, no one is completely sure where these are. Lawrence Livermore National Laboratory says radiation bursts found by the two Voyager spacecraft in 1993 may have been emitted at the shock point, placing the shock at somewhere between 130 and 170 astronomical units. An astronomical unit is a measurement equal to the average distance between the sun and Earth.
Significance
The pressure of the solar wind against the Earth's magnetosphere gives the magnetosphere its shape and creates geomagnetic storms and auroras. San Francisco's Exploratorium notes that the push from the solar wind creates a voltage, which in turn sends electrons hurtling toward the magnetic poles of the Earth. As the electrons begin to hit our atmosphere, they release light, creating the auroras. If the solar wind creates a lot of southward pressure on the magnetosphere, says the Naval Research Laboratory, this can create enough stress and disturbance in our atmosphere to form geomagnetic storms. These have the capability to take out power systems, as happened in Quebec in 1989, when a geomagnetic storm overloaded the electrical grid.
Investigation
NASA has launched several spacecraft meant to study the sun. Some have focused on the solar wind and others have investigated it as part of their duties. The Solar and Heliospheric Observatory, or SOHO, launched in 1995, and Spartan 201, launched in 1998, returned data that showed some solar wind particles may be "surfing on waves of the sun's magnetic field," notes Space.com. This phenomenon may answer why some areas of the solar wind were moving at much faster rates than expected. In 2001, NASA launched the Genesis spacecraft, which was to collect samples of solar wind particles and bring them back to Earth in 2004. NASA hoped the samples would provide information about the composition of the sun, or "solar nebula" as Space.com put it, back when the solar system was still forming. Unfortunately, the Genesis return capsule containing the samples went off course and crashed in Utah.
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