SSN SFI ? Understanding HF propagation reports by VE2XIP in PDF

 https://www.carc.cc/wp-content/uploads/2016/01/Understanding-HF-propagation-reports.pdf

https://www.voacap.com/ctu/propagation-ctu-en.pdf

https://www.f5uii.net/en/hamdxmap-propagation-muf-application-in-realtime-for-dxer/

https://www.swpc.noaa.gov/products/solar-cycle-progression

https://www.voacap.com/

https://dr2w.de/dx-propagation/

The SFI index or "Solar Flux Index" or "solar flux index" testifies to the activity of the sun towards the earth, at the same time ionizing the atmospheric layers, and therefore acting on the effects of propagation.

The higher the solar flux, the more the ionospheric layer will reflect HF waves.

The SFI values vary from 50 to 300 through which 3 propagation states can be determined depending on the SFI value:

from 100 to 150 . Good .

> 150 Better.

Values above 150 for 2 or 3 days result in ideal conditions for HF propagation.

The SN index also SSN or "SunSpot Number" or "number of sunspots or groups of sunspots" testifies to the number of spots visible on the surface of the sun.

The activity is very dense around sunspots and this has the effect of ionizing the layers of the ionosphere resulting in better reflection at high frequencies.

This index varies from 0 to 300.

bullet

Below 100, it is rather the low bands 3.6 MHz and 7 MHz that will be operational.

bullet

As soon as this index displays the value of 100, we agree that we have good HF propagation conditions.

bullet

From 150, the upper bands 24 MHz, 28 MHz and 50 MHz will allow "long distance" links

https://www.hamqsl.com/solar.html

https://www.facebook.com/SpaceWeatherLive

https://www.spaceweatherlive.com/en/solar-activity.html

The K and A indices.

These indices are used to quantify the geomagnetic activity of the earth. Intense geomagnetic activity, characterized by a high index, undoubtedly leads to poor HF radio conditions up to radio silence also called "black out" due to the attenuation of radio waves in the ionosphere.

 

  - The K index determines a geomagnetic activity recorded every 3 hours. This index therefore represents the activity of the last few hours, it indicates a short-term trend. Its scale varies from 0 to 9 and is interpreted as follows:

 

bullet

Between 0 and 3 Better conditions, the magnetic field is stable, the band noise is low, good propagation.

bullet

Between 3 and 5 Average conditions, low magnetic activity, the HF band is affected by band noise, propagation is slightly degraded.

bullet

Between 5 and 9 Poor conditions, strong magnetic activity or magnetic storm, strong band noise, poor propagation.

- The A index determines the average geomagnetic activity over 24 hours. It indicates a medium-term trend. Its scale is between 0 and 40 and is interpreted as follows:

 

bullet

Between 0 and 10 Excellent propagation conditions and low band noise.

bullet

Between 10 and 20 Average propagation conditions.

bullet

Between 20 and 40 Poor propagation conditions.

 

To conclude, the best DX HF conditions are obtained as soon as the solar flux index is above 150 for two or three consecutive days, an SN index also above 150 and finally with lower indices, for K at 3 and , for A to 10.

http://f4awt.free.fr/propagation.htm

https://www.contestuniversity.com/wp-content/uploads/2021/01/HF-Propagation-The-Rise-of-Solar-Cycle-25.pdf

https://www.qrparci.org/resource/FDIM81.pdf

https://en.wikipedia.org/wiki/Solar_cycle