Polar Cap Absorption

Term · Meteorology and atmospheric science · MLC-T-MET-002063

In solar-terrestrial terms, an anomalous condition of the polar ionosphere whereby HF and VHF (3 - 300 MHz) radiowaves are absorbed, and LF and VLF (3 - 300 kHz) radiowaves are reflected at lower altitudes than normal. In practice, the absorption is inferred from the proton flux at energies greater than 10 MeV, so that PCAs and
proton events are simultaneous. Transpolar radio paths may still be disturbed for days, up to weeks, following the end of a proton event.

Table 1. Record
Identifier	MLC-T-MET-002063
Field	Meteorology and atmospheric science
Abbreviation	PCA
References	NWS Glossary

Record as JSON

{
  "id": "MLC-T-MET-002063",
  "term": "Polar Cap Absorption",
  "field": "Meteorology and atmospheric science",
  "definition": "In solar-terrestrial terms, an anomalous condition of the polar ionosphere whereby HF and VHF (3 - 300 MHz) radiowaves are absorbed, and LF and VLF (3 - 300 kHz) radiowaves are reflected at lower altitudes than normal. In practice, the absorption is inferred from the proton flux at energies greater than 10 MeV, so that PCAs and\nproton events are simultaneous. Transpolar radio paths may still be disturbed for days, up to weeks, following the end of a proton event.",
  "abbreviation": "PCA",
  "references": [
    "NWS Glossary"
  ],
  "url": "https://mlchart.com/terminology/meteorology/polar-cap-absorption/"
}

Record 2,062 of 3,164 in Meteorology and atmospheric science terminology (MLC-0110). Request the full dataset.