A Floral Aurora Corona (2009 July 28 )
Posted: Tue Jul 28, 2009 4:37 am
Say "A Floral Aurora Corona" five times fast.
---------------------------------------------http://en.wikipedia.org/wiki/Aurora_(astronomy) wrote:
<<Bright auroras are generally associated with Birkeland currents which flow down into the ionosphere on one side of the pole and out on the other. In between, some of the current connects directly through the ionospheric E layer (125 km); the rest ("region 2") detours, leaving again through field lines closer to the equator and closing through the "partial ring current" carried by magnetically trapped plasma. The ionosphere is an ohmic conductor, so such currents require a driving voltage, which some dynamo mechanism can supply. Electric field probes in orbit above the polar cap suggest voltages of the order of 40,000 volts, rising up to more than 200,000 volts during intense magnetic storms.
A Birkeland current is a specific magnetic field aligned current in the Earth’s magnetosphere which flows from the magnetotail towards the Earth on the dawn side and in the other direction on the dusk side of the magnetosphere. In the Earth’s magnetosphere, these currents are driven by changes in the topology of the magnetotail (e.g. during substorms) and when they reach the upper atmosphere, they create the aurora Borealis and Australis. The currents are closed through the auroral electrojet, which flows perpendicular to the local magnetic field in the ionosphere.
Most auroras are green and red emissions from atomic oxygen.
Molecular nitrogen and nitrogen ions produce some low level red (pink) and very high blue/violet auroras.
The light blue and green colors are produced by ionic nitrogen
and the neutral helium gives off the purple colour whereas
neon is responsible for the rare orange flares with the rippled edges.>>
http://antwrp.gsfc.nasa.gov/apod/ap070715.html wrote:
<<Explanation: From the ground, spectacular auroras seem to dance high above. But the International Space Station (ISS) orbits at nearly the same height as many auroras, sometimes passing over them, and sometimes right through them. Still, the auroral electron and proton streams pose no direct danger to the ISS. In 2003, ISS Science Officer Don Pettit captured the green aurora, pictured above in a digitally sharpened image. From orbit, Pettit reported that changing auroras appeared to crawl around like giant green amoebas. Over 300 kilometers below, the Manicouagan Impact Crater can be seen in northern Canada, planet Earth.>>
