A dark croissant-shaped hole opened up in the sun's atmosphere, and spewed a stream of solar wind into space. NASA's Solar Dynamics Observatory took this picture of the vast opening during the early hours of January 30, 2011. Coronal holes are regions where the sun's corona is dark. These features were discovered when X-ray telescopes were first flown above the Earth's atmosphere to reveal the structure of the corona across the solar disc. Coronal holes are associated with 'open' magnetic field lines and are often found at the sun’s poles. The high-speed solar wind is known to originate in coronal holes.
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| Credit: NASA/SDO/AIA |
Normally, loops of magnetic energy keep much of the Sun’s outward flow of gas contained. Coronal holes are regions — sometimes very large regions, such as the one witnessed above — where the magnetic fields don’t loop back onto the Sun but instead stream outwards, creating channels for solar material to escape.
The material constantly flowing outward is called the solar wind, which typically “blows” at around 250 miles (400 km) per second. When a coronal hole is present, though, the wind speed can double to nearly 500 miles (800 km) per second.
Increased geomagnetic activity and even geomagnetic storms may occur once the gustier solar wind reaches Earth, possibly within two to three days.
The holes appear dark in SDO images because they are cooler than the rest of the corona, which is extremely hot — around 1,000,000 C (1,800,000 F)!
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| Credit: NASA/SDO/AIA |
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| Credit: NASA/SDO/AIA |
An enormous triangular hole in the Sun’s corona was captured on March 30, 2012 by NASA’s Solar Dynamics Observatory, seen above from the AIA channel 193.
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| Credit: NASA/SDO/AIA |
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| Credit: NASA/SDO/AIA |
Sources:
- Spaceweather.com
- Jason Major, Huge Coronal Hole Is Sending Solar Wind Our Way, Universe Today, March 13, 2012
- Solar Dynamics Observatory AIA Data Archive
- Coronal Hole in the Sun, NASA Image of the Day, June 5, 2012
