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Solar Terrestrial Data for HF Propagation

Mar 20th 2018, 15:35


Joined: Nov 7th 2003, 10:54
Total Topics: 0
Total Posts: 0
On the solar-terrestrial data for HF propagation ( ) reference by a good number of Ham Radio web site there is the Ef value. Unlike the other solar-terrestrial data posted I have not found anything that clearly defines what is a good or bad Ef value. Last Monday Ef was 1190 later that afternoon Ef it climbed to 15,100, and today Ef is 15,500 at 20:25 utc.

I’ve reviewed the attached NOAA web site along with a number of other web sites about Ef and I have not seen anything about these numbers. The only thing that come closes was NOAA Space Weather Alerts ( Electron Flux Alert “…when electron fluxes have exceeded the event threshold (1000 pfu)…”

So, should I assume anything over 1000pfu is bad (mean Ef 1190 is bad) and if yes what’s say about Ef 15,500 I’ve seen twice this week?

Already know Ef is short for Electron Fluxes, what I don’t know is this Ef values I see posted on the solar-terrestrial data is good or bad? And what is the worst case Ef value?

Any assistance would be appreciated
Mar 20th 2018, 21:39


Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
This page says that a high electron flux indicates poor propagation in polar regions. Which means that you shouldn't expect your signal to get past the North or South Poles.

Zak W1VT
ARRL Senior Lab Engineer

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