The Northern Lights

Like most planets, Earth has a magnetic field. Thank you, Earth’s molten iron core for making that happen for us. The magnetic field protects the planet from harsh radiation and dangerous solar winds—like we said, thank you. The magnetic field easily deflects these solar winds, mostly made of electrons and protons spewed out from the sun.

Remember the Lorentz force? Charged particles moving in magnetic fields experience a force perpendicular to them both, and in the case of the earth it means away. Occasionally though, energetic particles do make it through though and they become trapped moving in helical motion along the field back and forth between the north and south poles. These ions comprise the Van Allen radiation belts.

Not that we’ve ever heard of that. Here’s a picture.

When ions from the belts collide with the atmosphere of the Earth, fireworks occur. Particles in the atmosphere become ionized or excited. This produces the emission of bright lights in the sky, depending on what emissions and absorptions are taking place.

For example, oxygen atoms will emit green or reddish brown light, depending on the amount of energy released as an energized electron returns to its ground state. The difference in energy levels corresponds to different wavelengths of electromagnetic waves, or light.

Nitrogen, as a second example, emits blue light when absorbing an electron after having lost one to ionization. In the same atom, if an energized electron returns to the ground state, then it emits red light. Nitrogen is some 80% of the atmosphere, so the Northern Lights frequently show these colors in addition to those from oxygen.

No matter the colors, we guarantee a breathtaking show full of spectacular colors, and definitely worthy of taking a trip up north for the aurora borealis, or down south for the aurora australis.