Borealis Lighted
Where and when do the Northern Lights “Aurora Borealis”, happen?
In and near the Arctic Circle Aurora borealis.The aurora borealis most often occurs from September to October and March to April. The aurora is now known to be caused by electrons of typical energy of 1-15 keV, i.e. the energy obtained by the electrons passing through a voltage difference of 1,000-15,000 volts. The light is produced when they collide with atoms of the upper atmosphere, typically at altitudes of 80-150 km. It tends to be dominated by emissions of atomic oxygen--the greenish line at 557.7 nm and (especially with electrons of lower energy and higher altitude) the dark-red line at 630.0 nm. Both these represent "forbidden" transitions of atomic oxygen from energy levels which (in absence of collisions) persist for a long time, accounting for the slow brightening and fading (0.5-1 sec) of auroral rays. Many other lines can also be observed, especially those of molecular nitrogen, and these vary much faster, revealing the true dynamic nature of the aurora.
 |
 NEW Firefly Borealis Illuminated Keyboard Sleek Slim Design Capture the Light $49.95 Time Remaining: 4d 23h 41m Buy It Now for only: $49.95 |