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]
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