How is the northern lights made?

[waterliyl]

Hello,

I was just looking up some pictures when I saw a picture of the northern lights. I was told that it was something to do with electricity? What actually happens up there?

Thanks

 

[DrClaude]

Did you look at Wikipedia?

http://en.wikipedia.org/wiki/Aurora_(astronomy )

 

[jambaugh]

• The sun is so hot that the surface gasses boil off as disassociated ions. The hydrogen's electrons are stripped free of their proton nuclei.
• When charged particle pass through a magnetic field they are pushed sideways to the B field. If the B field is extensive enough a particle moving perpendicular to it will move in a circle around the lines of force. But it can move freely along the lines. The typical case is in between and they spiral around the B field lines.
• Add to this some random motion from hitting other particles.

So when the sun's solar wind of electrons and protons hit the Earth's magnetic field it is stopped by the field as the particles are turned perp. to the field lines. This protects us from their energetic bombardment. They will however begin to spiral around the magnetic field along the lines moving toward the Earth's north and south magnetic poles. As they reach the atmosphere they react with the atmospheric atoms just like the electricity in a neon light creating excitations which produce radiation.

The solar wind is very thin so this light is usually very faint. But during times of high solar activity you get a thicker solar wind and brighter aurora. Also the field lines don't all meet exactly at the poles but are spread out so so you have an extensive aurora and not just a big bright point right over the magnetic poles. Finally there is some reaction of the magnetic field to the incoming current of charged particles so it causes the Earth's magnetic field to contort and fluctuate, enough so that during solar "storms" this fluctuation can induce currents in power lines causing problems with electrical power distribution.