Green Light!
Last night the Finnish Lapland turned green. Photographer B.Art Braafhart of Sala, Finland, documented the event with a short exposure on his digital camera:
"To the naked eye, it was more of a light background color," says Braafhart, "but green is green!"
The green color of auroras is a sign of molecular oxygen. When solar wind and magnetospheric electrons rain down on the upper atmosphere, they strike atoms and molecules in the air. Different species produce different colors: O2 glows green, N2 purple, and O red. Although nitrogen is more abundant than oxygen in Earth's atmosphere, the green glow of excited O2 is so intense (relatively speaking) that it often overwhelms the other colors.
More green lights are in the offing. NOAA forecasters estimate a 25% chance of polar geomagnetic storms on Sept. 5 and 6 when a solar wind stream is expected to buffet Earth's magnetic field.
No comments:
Post a Comment