The Source of the High-Speed Solar Wind
Click on the image for a larger version.
Also available: High-resolution TIFF image. Variation on the above image:
Caption: Like water gushing through cracks in a dam, "fountains" of electrified gas, called the solar wind, has been observed by scientists flowing around magnetic regions on the Sun to begin their 3 million kilometres per hour rush into space. Scientists have identified regions on the Sun where the high speed solar wind - a stream of electrified gas affecting Earth's space environment - originates. Using ESA's Solar and Heliospheric Observatory (SOHO) spacecraft, American and European scientists, have observed solar wind flows coming from the edges of honeycomb-shaped patterns of magnetic fields at the surface of the Sun. These observations are presented in the 5 February issue of Science magazine. The research will lead to better understanding of the high-speed solar wind, a stream of electrified gas that affects the Earth's space environment.
The "zoomed-in" or "close-up" region in the image above shows a Doppler velocity map of million degree gas at the base of the corona (solar atmosphere), where the solar wind originates. Blue represents blue shifts or outflows and red represents red shfts or downflows. The atmospheric motion toward us, away from the solar surface, is seen as a blue shift, and is the beginning of the solar wind.The blue regions are inside a coronal hole, or open magnetic field region, where the high speed solar wind is accelerated. Superposed are the edges of "honey-comb" shaped patterns of magnetic fields at the surface of the Sun, where the strongest flows (dark blue) occur. These flows begin at 20,000 mph at the surface, and accelerate to over a million mph as they stream toward the Earth.
The solar wind comes in two varieties : high-speed and low-speed. The low-speed solar wind moves at "only" 1.5 million kilometres per hour, while the high-speed wind is even faster, moving at speeds as high as 3 million kilometres per hour.
As it flows past Earth, the solar wind changes the shape and structure of the Earth's magnetic field. In the past, the solar wind didn't affect us directly, but as we become increasingly dependent on advanced technology, we become more susceptible to its effects. Researchers are learning that variations in the solar wind flow can cause dramatic changes in the shape of the Earth's magnetic field, which can damage satellites and disrupt communications and electrical power systems.
Solar Ultraviolet Measurements of Emitted Radiation
(SUMER); Extreme ultraviolet Imaging Telescope (EIT);
Taken: 26 September 1996
Picture credit: SOHO/SUMER and SOHO/EIT (ESA and NASA)