The LIVE report to the left uses terms such as SFI, SN, N, K, A. What do they mean? Here is a quick check sheet of what they mean to amateur radio propagation.

SFI index: Solar Flux Index: the higher the number, the better HF propagation show be on bands between 10 meter and 20 meter (ie: 10m,12m,15m,17m,20m). High SFI values has almost no influence on 30m,40m,80m and 160m bands.

It has a scale between 30 and 300, and can be interpreted as follow:

  • Less than 70: propagation potentially bad.
  • 80-90: propagation potentially are somewhat low
  • 90-100: propagation tend to be average
  • 100-150: propagation will tend to be good
  • Greater than 150: propagation will tend to be ideal

SN: Sunspot Numbers:  the higher the number, the better the ionization of our atmosphere which will help create great HF propagation conditions. The range of SN can be between 0 and up to 250

SN numbers can be interpreted as follow:

  • Less than 50: propagation conditions potentially very bad
  • 50-75: propagation conditions attenuated 75-100: propagation conditions might be good
  • 100-150: propagation conditions should be ideal
  • Greater than150: propagation conditions possibly exceptional

 The A Index: You should use this as a reference for general conditions on the bands. Lower A index means better conditions for propagation. This score goes between 0 and 400, but typically never above 100.

This value should be interpreted as follows:

  • Between 1 and 5: Best conditions on 10,12,15,17,20 meter bands.
  • Between 6 and 9: Average conditions on 10,12,15,17,20 meter bands.
  • From 10 and above: Very Bad conditions on 10,12,15,17,20 meter bands. 

The Ap-index value can be interpreted as follow:

  • Between 1 and 5: Best conditions expected on 30,40,80,160 meter bands.
  • Between 6 and 9: Average conditions expected on 30,40,80,160 meter bands.
  • From 10 and above: Bad conditions expected on 30,40,80,160 meter bands.

The K-Index Falling numbers mean improving conditions and better propagation particularly in northern latitudes and areas where aurora activity can occur. The scale is between 0 and 9. You never want to see value above 8, this indicates our planet going thru a solar storm of great intensity.

This value can be interpreted as follow:

  • From 0 to 1: Best conditions for 10,12,15,17,20 meter bands.
  • From 2 to 3: Good conditions for 10,12,15,17,20 meter bands.
  • From 4 to 5: average conditions for 10,12,15,17,20 meter bands.
  • From 5 to 9: Very bad conditions for 10,12,15,17,20 meter bands.

The Kp-index value can be interpreted as follow:

  • Between 0 and 1: Best conditions expected on 30,40,80,160 meter bands.
  • Between 2 and 4: Good conditions expected on 30,40,80,160 meter bands.
  • Between 5 and 9: Bad conditions expected on 30,40,80,160 meter bands. 

X-Ray: NOAA reported value from A0.0 to X9.9. Intensity of hard x-rays hitting the earth’s ionosphere. Impacts primarily the D-layer (HF absorption). The letter indicates the order of magnitude of the X-rays (A, B, C, M and X), where A is the lowest. The number further defines the level of radiation. Updated eight times daily.

304A: NOAA reported value from 0 to unknown. Relative strength of total solar radiation at a wavelength of 304 angstroms (or 30.4 nm), emitted primarily by ionized helium in the sun’s photosphere. Two measurements are available for this parameter, one measured by the Solar Dynamics Observatory, using the EVE instrument, and the other, using data from the SOHO satellite, using its SEM instrument. Responsible for about half of all the ionization of the F layer in the ionosphere. 304A does loosely correlate to SFI. 

Ptn Flx: NOAA reported value from 0 to unknown. Density of charged protons in the solar wind. The higher the numbers, the more the impact the ionosphere. Primarily impacts the E-Layer of the ionosphere.

Elc Flx: NOAA reported value from 0 to unknown. Density of charged electrons in the solar wind. The higher the numbers (>1000), the more the impact the ionosphere. Primarily impacts the E-Layer of the ionosphere.

N: NOAA reported value from 0 to 5. When <2.0, high confidence in Aurora measurement. When >2, low confidence.