Steven M London +1 303 538 4763
Steven.M.London at att.com
Wed Sep 15 09:09:40 EDT 1993
Here's my empirical insights on sunspots and propagation, based on 3 cycles
worth of operating.
The last sunspot cycle did indeed bottom out in late 1986,
based on smoothed sunspot numbers. However, if you look at monthly
averages, we were essentially at the bottom from late 1984 until early
1987. The current cycle does seem to be in a hurry to get to the bottom.
If anyone is interested, I'll post the monthly averages for the last
The lowest daily solar flux values were 66 in cycle 20, and 67 in cycle 22.
However, in both cycles weeks went by where the flux didn't exceed 70.
The day-to-day variability in the solar flux is far less at the bottom
than it was at the top of the cycle. At the bottom of the cycle, a 5
point rise (or fall) in a day is very large. On the optimistic side,
all it takes is one medium size sunspot group to raise the flux from 70
to 85 or 90. Look at CQWW Phone, 1985 and 1986 for examples.
>From a Colorado perspective, I find that 15 meters is very sensitive to
the solar flux number. It is rare to have a decent JA or EU opening with the
flux less than 75, but during the fall/winter/spring season, 15 will play
very well with a flux of 85 and undisturbed condx. I also find the
nighttime MUF to be sensitive to the flux. With a flux less than
90, and wintertime condx, the nighttime MUF drops below 40 meters to EU
and JA. We end up with short openings at sunrise/sunset at each end of
the path, and work nothing but Africa, South America and the South Pacific
I don't claim to be a solar-terrestrial expert - just a lot of experience
through a few sunspot cycles.
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