SFI index: Solar Flux Index. it is a gauge of how much solar particles and magnetic fields reaching our atmosphere. In other words, this value informs us on solar winds reaching our planet and their influence on creating HF propagation conditions. For this measurement, the higher the number, the better HF propagation show be. The index value also suggest propagation on bands between 10 meter and 20 meter (ie: 10m,12m,15m,17m,20m). It has a scale between 30 and 300, and can be interpreted as follow:
< 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
>150: propagation will tend to be ideal
High SFI values has almost no influence on 30m,40m,80m and 160m bands. SFI value over 150 indicates ideal HF propagation conditions and people with small HF installations can begin exploiting these conditions. At these high SFI values, we might take advantage of these conditions while they last because they are far and few between. It might be here today, gone tomorrow.
SN: Sunspot Numbers. This value is the visible number of spots on the Sun’s surface. Traditionally, 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, sometimes more. It is somewhat rare that we see over 200 sun spots, and when we do, it might be an ideal time to turn on your Transceiver!
High SN numbers indicate large amounts of electromagnetic active fields on the surface of the Sun, potentially erupting as solar flares, but before they erupt into solar flares, they can create excellent HF propagation. If Sun spots turn into flares, this can diminish substantially HF propagation, even create total radio blackouts on all bands. Also, knowing that the Sun’s equator rotates on itself, the Sun spots and its fields may or may not be facing us at all times. This said, radio propagation conditions could become excellent for a few days, then down until the Sun rotate those spots back toward us again, which is between 18-25 days later.
So, if you see SN numbers over 100, you can expect good propagation conditions, if and when these spots are facing us. The current Solar Maximum is 2013 but solar activities have not been as high as expected. It’s part of the hobby, we’ll just take what we can get !
During solar minimums (Low or no sun spots), you can see bad or absent propagation conditions going on for years at a time, and this until the next solar cycle. When these conditions occur, Amateur Radio operators often revert back to using lower frequencies (ie: 30m,40m,60m,80 and 160m), and watch for events that will to create temporary propagation conditions, such as sun rise and sun sets. When conditions were poor, make your furthest contacts when the Sun was rising or when it was setting. SN numbers can be interpreted as follow:
< 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
>150: propagation conditions possibly exceptional
The A Index: It’s simply an index of geomagnetic activity derived from a scaled average of the previous 24 hours K-index readings. Your should use this as a reference for general conditions on the bands. Lower A index means better conditions for propagation. This scare goes between 0 and 400, but typically never above 100. This value should be interpreted as follow:
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 (or Boulder K)is a gauge of geomagnetic activity relative to an assumed quiet-day. 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 because 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. Updated hourly.
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. Updated hourly.
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. Updated hourly.
N: NOAA reported value from 0 to 5. When <2.0, high confidence in Aurora measurement. When >2, low confidence. Updated hourly.