"Aurora had but newly chased the night,
And purpled o'er the sky with blushing light."
~John Dryden (1631-1700), Palamon and Arcite
The Aurora's glow comes from collisions between fast moving electrons from the magnetosphere (the region of space controlled by Earth’s magnetic field) and oxygen and nitrogen molecules in our upper atmosphere. Large number of collisions result in light of many colors: Oxygen emits greenish-yellow or red light, while nitrogen generally gives off blue light; and the blending of these produces purple, pink, and white. Some North American Inuit call the auroras aqsarniit, or football players, believing they result from spirits of the dead playing football with the head of a walrus!
This month marks the beginning of the many festivals in Scandinavia to celebrate the Northern Lights.
Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind, which carries charged particles mainly in the form of electrons and protons, and precipitates them into the upper atmosphere (thermosphere/exosphere), where their energy is lost.
The resulting ionization and excitation of atmospheric constituents emits light of varying colour and complexity. Aurora colors can be red, green, blue, ultraviolet and infrared (measurable), yellow and pink.
Auroras are thought by some to emit a crackling noise, though scientists disagree as to whether this is a real phenomenon given that where the lights occur is too thin to carry sound waves. Early explorers found that covering eyes made the sound disappear, so the researches now suggests that the perception of sound could be caused by "signal leakage" from overstimulated visual centers in the brain or by energetic phenomena associated with the aurora.
This tartan was inspired by the Aurora Borealis in the night sky, frequently seen in Norway. The colours used are: red, blue and white from the Norwegian flag; yellow, white and black are for the Aurora Borealis in the night sky (polar light).
The beautiful picture of the Aurora was taken at Hammerfest, Finnmark, Norway, by Per-Andre Hoffman. For more Aurora photography, visit his site by clicking the picture.