Solar flux are high-energy particles from the sun correlated to the number of Sunspots. High solar flux can cause degradation and polar cap blackouts of HF radio.

The K index is a measure of the range of geomagnetic polar storms caused by the sun on a non-linear 0-9 scale.

The A index is a daily geomagnetic activity average based on the K index converted to a linear 0-400 scale.

Conditions is a summary of HF band propagation: Very poor, Poor, Fair, Normal, Good or Excellent.

Note: For prediction of HF propagation between any two points use VOACAP (Voice of America Coverage Analysis Program) with the VOAProp presentation engine.

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