# Aurora borealis

• I

## Main Question or Discussion Point

How do the northern lights work?

I have already know why it emits light, but why in waves? Why does it move? Are the particles that excite oxygen the ones that were deflected, or the ones that were already heading straight towards the Arctic Circle? Feel free to post any questions as they come up and I'll edit it into the post.

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jambaugh
Gold Member
The waves in the aurora reflect waves in the Earth's magnetic field. The particle spiral in along the magnetic lines of force and the aurora forms as they impinge upon the atmosphere.

As a charged particle moves in a magnetic field its component of motion along the field line is unchanged but the perp. component is rotated about the field line. A particle moving perp to a uniform field will move in a circle, if it's moving parallel it moves in a straight line. The usual mixture of perp and parallel components yields a helical motion. In general the axis of motion will be exactly along a field line but collisions allows ions to "jump" to another field line orbit.

Also since the moving charged particles constitute an electric current, they will contribute to the magnetic field themselves if the particle flux is significant you can get some rather complex interaction between magnetic field and this plasma. (Note how volatile and chaotic the sun's surface can become!)

That's the gist of what I understand about them, someone more dedicated to their study could give you far more info I'm sure.

The waves in the aurora reflect waves in the Earth's magnetic field. The particle spiral in along the magnetic lines of force and the aurora forms as they impinge upon the atmosphere.

As a charged particle moves in a magnetic field its component of motion along the field line is unchanged but the perp. component is rotated about the field line. A particle moving perp to a uniform field will move in a circle, if it's moving parallel it moves in a straight line. The usual mixture of perp and parallel components yields a helical motion. In general the axis of motion will be exactly along a field line but collisions allows ions to "jump" to another field line orbit.

Also since the moving charged particles constitute an electric current, they will contribute to the magnetic field themselves if the particle flux is significant you can get some rather complex interaction between magnetic field and this plasma. (Note how volatile and chaotic the sun's surface can become!)

That's the gist of what I understand about them, someone more dedicated to their study could give you far more info I'm sure.
Would be excited to see if anyone could expand on this, thanks a lot.

anorlunda
Mentor
Have you seen videos of solar prominences? They are very dynamic. It would be reasonable therefore to expect the solar wind to arrive at Earth in puffs, and waves, with varying speeds and directions. Those small variations should cause corresponding variations in the aurora. I visualize the analogy of sunlight reflected from the surface of a choppy sea.

Have you seen videos of solar prominences? They are very dynamic. It would be reasonable therefore to expect the solar wind to arrive at Earth in puffs, and waves, with varying speeds and directions. Those small variations should cause corresponding variations in the aurora. I visualize the analogy of sunlight reflected from the surface of a choppy sea.

Ah, that is what I figured but I wasnt so sure about it. Now I'm more certain, thanks!