What’s behind the dark spots in the sun’s atmosphere?
The sun’s magnetic field wreaks havoc on the solar atmosphere. At times the magnetic field lines that rise and fall from the surface in giant arcs can become detached at one end. When this happens, a ghostly patch develops in the sun’s upper atmosphere creating what’s known as a coronal hole. Viewed at certain wavelengths, the hole appears black as if it were empty. But, in fact, these holes are a source of strong solar wind, where streams of energized particles shoot out into space. If a hole points toward Earth, a bombardment of particles will reach the planet within two or three days, sometimes resulting in aurorae. NASA’s Solar Dynamics Observatory, or SDO, spacecraft has observed many coronal holes since its launch in 2010. Watch the video for a close look at one discovered in May 2014.