SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hame-polar-cap-absorption

What happens during a polar cap absorption event?

Radio waves get absorbed over the polar regions.

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  1. HF and VHF waves are absorbed over the polar ionosphere ✔
  2. Polar paths become the best routes for HF
  3. The E layer disappears worldwide

Why: NOAA's glossary describes polar cap absorption as an anomalous condition of the polar ionosphere where HF and VHF radio waves are absorbed. Polar paths can go dead for HF.

Huh, didn't know that: Solar radiation storms can block HF radio at high latitudes.

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References

Answer: HF and VHF waves are absorbed over the polar ionosphere. NOAA's glossary describes polar cap absorption as an anomalous condition of the polar ionosphere where HF and VHF radio waves are absorbed. Polar paths can go dead for HF.

  1. NOAA SWPC Space Weather Glossary www.spaceweather.gov/content/space-weather-glossary
    where HF and VHF (3-300 MHz) radiowaves are absorbed
    Checked 2026-10-11.
  2. NOAA SWPC HF Radio Communications www.spaceweather.gov/impacts/hf-radio-communications
    blocking HF radio communication at high latitudes
    Checked 2026-10-11.

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