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Aurora As Seen From Space: Earth Image of the Week July 9, 2010
Astronaut photo of aurora australis.
Aurora happen when ions in the solar wind collide with atoms of oxygen and nitrogen in the upper atmosphere.
Among the views of Earth afforded astronauts aboard the International Space Station, one of the most spectacular is of the aurora.

These ever-shifting displays of colored ribbons, curtains, rays, and spots are most visible near the poles.

They’re called the aurora borealis in the Northern Hemisphere and the aurora australis when seen south of the equator. The aurora are illuminated when charged particles streaming from the sun interact with Earth’s magnetic field. This solar wind is comprised of ions.

While aurora are generally only visible close to the poles, severe magnetic storms impacting the Earth’s magnetic field can shift them southward toward the highly populated middle latitudes.

This striking aurora image to the right was taken during a geomagnetic storm that was most likely caused by a coronal mass ejection from the sun on May 24, 2010.

The ISS was located over the southern Indian Ocean at an altitude of 220 miles on May 29 when the image was captured on a digital camera. The astronaut observer who took the photo was most likely looking southward towards Antarctica and the South Pole.

The aurora has a sinuous ribbon shape that separates into discrete spots near the lower right corner of the image.

While the dominant coloration of the aurora is green, there are faint suggestions of red left of image center. Dense cloud cover is dimly visible below as it was being illuminated by the aurora.

The curvature of the Earth’s horizon is clearly visible, as is the faint blue line of the upper atmosphere directly above it, more discernible in the enlarged version of the photo. Several stars appear as bright pinpoints against the blackness of space at image top right.

Full story and image: NASA