Green Aurora Seen from the Space Station
As geomagnetic storms cause beautiful displays of aurora across the United States (related story on CNN), astronauts onboard the International Space Station also have the opportunity to take a look. Green colors of the aurora are dominant in this image captured by a digital still camera on October 4, 2001. Auroras are caused when high-energy electrons pour down from the Earth’s magnetosphere and collide with atoms. Green aurora occurs from about 100 km to 250 km altitude and is caused by the emission of 5577 Angstrom wavelength light from oxygen atoms. The light is emitted when the atoms return to their original unexcited state.
At times of peaks in solar activity, there are more geomagnetic storms and this increases the auroral activity viewed on Earth and by astronauts from orbit. By using a digital camera with a long exposure time, astronauts can capture a part of the light from the multicolored displays they observe, and downlink those images to Earth.
Information and forecasts of geomagnetic activity and aurora observations can be found at http://spaceweather.com/.