NASA spots giant coronal hole on Sun

NASA's Solar Dynamics Observatory has spotted a giant dark area on the upper half of the Sun known as a coronal hole.
Coronal holes are areas on the Sun where the solar magnetic field extends up and out into interplanetary space, sending solar material speeding out in a high-speed stream of solar wind.
Scientists study these fast solar wind streams because they sometimes interact with Earth's magnetic field, creating what is called a geomagnetic storm, which can expose satellites to radiation and interfere with communications signals.
Coronal holes are low-density regions of the Sun's atmosphere, known as the corona. They contain little solar material and have lower temperatures, thus appearing much darker than their surroundings, researchers said.

Coronal holes are visible in certain types of extreme ultraviolet light, which is typically invisible to our eyes.
These coronal holes are important to understand the space environment around Earth through which technology and astronauts travel, NASA said.
Coronal holes are the source of a high-speed wind of solar particles that streams off the Sun around three times faster than the slower wind elsewhere.
While it is unclear what causes coronal holes, they correlate to areas on the Sun where magnetic fields soar up and away, without looping back down to the surface, as they do elsewhere, researchers said.