|Northern Lights over Lyngen fjord, March 2012.|
Auroras occur because of solar winds. Solar winds are highly charged electrons blown from the Sun toward the Earth. Streams of charged particles, called plasma, escape the Sun's gravity because of their high energy (1.5 to 10 KeV).
“A man is a very small thing, and the night is very large and full of wonders.”Solar winds flow at supersonic speeds outward from the Sun covering great distances and creating geomagnetic storms in the Earth's magnetosphere.
― Lord Dunsany
|Depiction of solar wind particles interacting with Earth's magnetosphere.|
When the highly charged electrons enter the Earth's upper atmosphere they encounter oxygen and nitrogen at various altitudes. Color in Northern Lights is determined by whether oxygen or nitrogen atoms are struck first and at what altitude.
|Color||Gas||Alt. (km)||Alt. (miles)|
up to 240
up to 150
up to 97
up to 60
Shifting combinations of charged particles encountering atmospheric gases at various altitudes make the Northern Lights undulate and dance in the night sky.
The core and the surface
Are essentially the same,
Words make them seem different
Only to express appearance.
If name be needed, wonder names them both:
From wonder into wonder
― Lao Tzu, translated by Witter Bynner
- Aurora, Wikipedia.
- Northern Lights Mythology & Science, GrokEarth, 24 March 2012.
- Solar Wind, Wikipedia.