Chapter 17 Section B: Outer Layer Phenomena

Aurora Borealis and Aurora Australis
1. Solar flares (violent eruptions on the surface of the sun) eject electrons and protons into space.
2. These particles collide with molecules in Earth's upper atmosphere.
3. The collisions cause them to become ionized and electronically excited.
4. The excited ions return to the ground state.
5. This process emits light, creating auroras.

- The solar particles are oriented by Earth's magnetic field so that most displays occur in
- donut-shaped zones about 2000km in diameter centered on the North and South Poles
- Aurora borealis: Northern Hemisphere
- Aurora australis: Southern Hemisphere
- Auroras can disrupt radio transmission

* = electronically excited species
hv = emitted photon

Ex: O* → O + hv
hv = 558nm (green) and 630 - 636nm (red)
Ex2: N2+* → N2+ + hv
hv = 391 (violet) and 470nm (blue)


The Mystery Glow of Space Shuttles
- 1983: Astronauts noticed an eerie orange glow on outside surface of their spacecraft 300km above the earth
- This light extended 10cm away from the protective silica heat tiles of the shuttle
- The glow was most pronounced on the parts of the shuttle facing its direction of travel
- Scientists postulated it was caused by collisions between oxygen atoms in the atmosphere
- Later astronauts aboard the Discovery realized that oxygen interacts with nitric oxide

O + NO → NO2*
NO2* → NO2 + hv

NO2* emits photons at a wavelength of 680 nm (orange). The NO is from shuttle exhaust

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