Current Propagation Conditions!

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Solar Cycle Progression

This chart by Pete Greene, N2LVI, provides scale for some solar values. It does a good job of putting them in context, though based on other articles, it might be stingy in that sunspot numbers over 100 are generally considered very good on the higher bands:


SFI - Solar Flux Index: Measure of 2800 MHz radiation. Range 60 - 300. Correlates with UV and X-ray radiation.

SN - Sunspot Number: Also takes into account size and shape. Range 0 - 250. The higher the number, the more radiation ionizing our propagation layers.

A Index: Derived from the K index, measures the global value of geometric disturbance during the previous UTC day. Range 0 - 400.

K Index: Average current level of disturbance in Earth's magnetic field. Rising K means increasing instability. Above 4 indicates geomagnetic storm. Range logarithmic 0 - 9.

X-Ray Intensity: Responsible for ionization levels D and partially E layers, which can absorb signals. A high powered X-ray can absorb signals in the entire HF range causing an HF blackout. Classes, from weakest to strongest, are B, C, M and X.

304A: Correlates with SFI and measures radiation at a wavelength of 304 angstroms. This wavelength is responsible for about half the radiation of the F layer. The higher the number, the better the F layer propagation.

Ptn Flx - Proton Flux: Density of protons in Earth's magnetic field. Typically under 10, when over 10,000, signals over polar regions begin to degrade.

Elc Flx - Electron Flux: Similar to Proton Flux, auroral paths degrade when EF reaches 1000.

Aurora: Ranged from 1-10, a higher numbers indicate auroral activity is shifting to lower latitudes and the opportunity to see northern / southern lights increases. Can indicate improved propagation from 10M - 70cm, but may also indicate the presence of polar path HF blackouts.

MUF Boulder - Maximum Usable Frequency: The maximum usable frequency as measured at Boulder Colorado.

Geomag Field - Geomagnetic Field: Indicates how quiet or active the Earth's magnetic field currently is.

Sig Noise Lvl - Signal noise level: A measure of how much noise in S units is being generated as the solar wind interacts with Earth's magnetic field.