Space weather Operational Airline Risks Service (SOARS)
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D-Region Absorption (HF Communications)

Lower/Mid Latitudes Polar Region
Current HF Flags, from IPS
SWF Warning Current HF Fadeout Warning
SWF Event Current HF Fadeout Event
Current Activity Report, from SEC
Range 1 (minor) to 5 (extreme)
NOAA Scale
< Radio Blackouts
Radiation Storm >
SWF: [IPS ALF Plot] [IPS ALF - last major flare]     PCA: [IPS PCA Report] [Realtime Riometers]     Polar Maps: [1] [2] [3]

RF propagation in the HF (High-Frequency) band can be affected by two types of D-Region absorption event - in extreme conditons either type can produce a Radio Blackout:               [more - science]
  • At lower and mid latitudes, X-rays from solar flares can cause a Short Wave Fade (SWF) event;
  • In the auroral/polar zone, protons from a solar particle event can produce a Polar Cap Absorption (PCA) event.

The predicted effect of a SWF event is shown in upper plot, left panel (HAF Plot produced by SEC - see also ALF Plot produced by IPS); the current X-ray intensity is shown in the lower plot, left panel. The intensity of proton precipitation (upper plot, right panel) is a pointer to the likelyhood of a PCA event; the proton lightcurve (lower plot, right panel) shows the current conditions. [more - plots] [HF Propagation forecasts]