Aurora

I have just finished the Japanese drama, Last Christmas though there were few episodes are corrupted. It is indeed a nice drama. Both main actor and actress were great. Besides that, this drama gave me a warmth feeling after watching it. The caring and loving between the both actors were just nice. Sweet and nice. That’s it.

I have learnt something new from this drama. An unusual beautiful scene from the nature. AURORA. here are some cut and paste article from the web.

The aurora is a glow observed in the night sky, usually in the polar zone. It is also known as "northern lights" or "aurora borealis," which is Latin for "northern dawn" since in Europe especially, it often appears as a reddish glow on the northern horizon as if the sun were rising from an unusual direction. The aurora borealis most often occurs from September to October and March to April. Its southern counterpart "aurora australis," has similar properties, so scientists prefer "polar aurora" (or "aurora polaris").

Auroral mechanism
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 1000-15,000 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.

Auroras can also be observed in the ultra-violet (UV) light, a very good way of observing it from space (but not from ground--the atmosphere absorbs UV). The "Polar" spacecraft even observed it in X-rays. The image is very rough, but precipitation of high-energy electrons can be identified.



















Aurora in Japanese オーロラ
Aurora in Chinese 极光

Don't you think they are beautiful and unusual?!