Avid surfers habitually check the swell forecast to plan their next surf session. Those interested in the night sky, and who live in the far northern latitudes of our planet, frequently check the aurora forecast. The aurora borealis, or northern lights, are amazing both in terms of the visual displays they produce, and the explanation of their occurrence. Violent storms in the sun's atmosphere hurl electrons and protons towards earth at supersonic speeds. This solar wind of charged partials travels 150 million kilometers before battering earth's magnetosphere, a kind of protective shield generated by our planets iron-nickel core. Waves of charged particles are bent towards weak spots in this magnetic field at the poles, known as the magnetopause, and are allowed to penetrate earth's atmosphere. This is when the light show begins. Molecules in the atmosphere become excited, like the gas in a fluorescent bulb, and emit colorful bursts of light. Pale green is the most common color, caused by excited oxygen molecules in the lower atmosphere; while the occasional pinks and purples are the result of nitrogen molecules. The patterns created in the night sky during these solar events are infinitely complex and beautiful, from diffuse blotches to vibrant streaming curtains of light.
During extreme solar activity, northern lights can even be visible in some of the lower latitudes, so you might want to keep an eye on the following links.
http://origin-www.swpc.noaa.gov/products/30-minute-aurora-forecast
http://www.gi.alaska.edu/AuroraForecast
Canon EOS 60D, Bower 8mm f/3.5 Fisheye CS, ISO-1000 f/3.5 @ 8 sec
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