Astronauts aboard the space shuttle have long told tales of shimmering auroras flickering high above Earth’s atmosphere. Standard textbooks say that auroras cannot form at such rarefied heights, leading many scientists to doubt the reports. But a sun-spying satellite has now confirmed that the astronauts are right and the textbooks wrong.
The Solar Mass Ejection Imager satellite (SMEI), launched by the U.S. Air Force in January 2003, tracks giant bubbles of energized particles as they belch off the sun. Auroras usually occur when the most energetic of those particles flow down Earth’s magnetic field and collide with atmospheric atoms such as oxygen and nitrogen, which then emit light.
This process was thought to occur only at altitudes below about 60 miles, where there are enough atoms to produce a visible glow. But while poring over SMEI data collected during a solar outburst last May, research physicist Andrew Buffington of the ...
