Science · 6 pages · 12 min
How the ionosphere bounces some radio waves
Free electrons high in the air reflect some radio frequencies and pass others.
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From the opening
The ionosphere returns some radio waves because sunlight strips electrons from atoms high in the atmosphere, and that population of free electrons can act, for long enough wavelengths, like a reflecting layer. A signal sent upward at the right frequency can be turned back down beyond the horizon. The opening covers why free electrons turn a wave, why the cutoff changes after dark, and what a vertical sounding measures.
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Inside
- Why free electrons turn a wave
- Why the cutoff changes after dark
- What a vertical sounding measures
- When a disturbance kills the path
- Where the idea stops applying
- A distinction worth keeping
Sources
- Ionospheric reflection and the plasma cutoff
- The Kennelly-Heaviside layer