Last week, I talked about the spaceport Poker Flat, Alaska that launches rockets for research on the aurora.
In the Earth’s atmosphere, an electrically charged layer exists between 80 km and 400 km height. Here, molecules of nitrogen and oxygen, and oxygen atoms absorb X-rays and ultraviolet radiation coming from the Sun. In this process, the gas becomes excited, i.e. electrons jump to a higher orbit around their nucleus. Each affected molecule loses one or more of its electrons and then becomes a positively charged ion. Because of this ionization, this atmospheric layer is called the ionosphere.
When the electrons fall back to a lower orbit around the nuclei, the emitted radiation becomes visible as aurora. Auroras in the northern and southern hemisphere are called aurora borealis and aurora australis, respectively.
The different colors of the aurora depend on the emitting molecules and on the solar activity. Around 100 km or so, the emission by nitrogen molecules results in reddish fringes on the lower part of the aurora curtains. Between 100 to 300 km altitudes, emission by oxygen molecules causes the most frequent yellow-greenish auroras. Above 300 km height, the oxygen atom is the most common. Its emission produces the rare red aurora that in my 13 years in Alaska I saw only once. Even higher in the ionosphere, hydrogen and helium are the most frequent atmospheric components. When they emit radiation, we obtain bluish and purplish colors.
Next Monday I will explain why the aurora became of interest during WWII.
I am wearing my striped skirt c/o eShakti with my leather shell and a lace top underneath to add some insulation. The scarf is for styling of the outfit and repeats some of the skirt’s colors. The patent leather wedges pick up the beige and black of the outfit. For the commute to work I added my trench coat and Jaeger tote, which was a consignment find this summer.
Photos: G. Kramm
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