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ARRL Propagation Bulletin ARLP040 (2021)

ARLP040 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7RA
Seattle, WA  October 1, 2021
To all radio amateurs 

ARLP040 Propagation de K7RA

Sunspot activity was up over the past week, with the average daily
sunspot number rising from 28.7 to 59.4, and average daily solar
flux up 11.4 points to 89.8.

The noon 10.7 cm solar flux was 101.6 on Wednesday, September 29,
the highest value since December 3, 2020, when it was 102.9.
Unfortunately, the following day that value slipped seven whole
points back to 94.6

Geomagnetic indicators were quiet, with average daily planetary A
index values declining from 9.1 to 7.3, and average middle latitude
A index from 8.4 to 6.3.

Nice to see our Sun peppered with spots again as we move into the
second week of Fall in the northern hemisphere.

Predicted solar flux as of Thursday is much lower than it was the
day before.

The updated flux values are 95 on October 1-3, 90 on October 4-5, 85
on October 6-7, 74 on October 8-9, 78 on October 10-12, 80 non
October 13, 84 on October 14-15, 86 on October 16-17, 88 on October
18-22, 86 on October 23-25, 84 on October 26, 80 on October 27-29,
78 on October 30-31, 76 on November 1, and 74 on November 2-5.

Flux values may rise back to 88 by mid-November.

Predicted planetary A index is 24, 10 and 8 on October 1-3, 5 on
October 4-9, 12 on October 10, 5 again on October 11-17, then 10,
12, 10 and 8 on October 18-21, 5 on October 22-23, then 18, 15 and
12 on October 24-26, 5 on October 27-30, 8 on October 31, 12 on
November 1, and 5 on November 2-5, then 12 on November 6.

Geomagnetic activity forecast for the period October 1-26, 2021 from
F.K. Janda, OK1HH.
"Geomagnetic field will be:
quiet on: October 13, 16-18, 22-23,
quiet to unsettled on: October 3-4, 6-9, 12, 20-21,
quiet to active on: October 2, 5, 10- 11, 14-15,
unsettled to active on: October 1, (19, 24-26)
Active to disturbed: Nothing predicted.
"Solar wind will intensify on October (3,) 11, (19, 22-23, 25).
- Parenthesis means lower probability of activity enhancement.
- Contradictory indications currently reduce the accuracy of the

I often use FT8 and to check propagation
on different bands, and over the past week there were days when I
saw no reception reports of my station on 10 meters, but plenty of
activity on 12 meters. The 12 meter openings were typically to
stations 2,000 miles to the east of me, over a narrow swath along
the eastern seaboard of North America. This was with a very simple
end-fed non-resonant wire antenna and 30 watts of output power.

Check this link about Sunspot, New Mexico:

Bob, AA6XE, sent this:

"September 2021 is winding down and here is a preview of the solar
numbers we can expect this Friday. The solar flux for September
looks to be 86.5 measured and 88 adjusted for 1 AU. This is the
second highest reading of the new solar cycle topped only by the
dramatic run-up last November. Take a good long last look at those
numbers as the current ramp-up in solar activity will easily blast
through them in October. In the closing 36 hours of the month the
10.7 cm solar flux had jumped up 12 points to 101 and was rising
fast as this report was being typed up.

"The Monthly Mean Sunspot Number for September will be in the low to
mid 50s (new scale), say 54 (new scale) when converted to the old
scale, so when we can compare it to traditional counts it equates to
38 (old scale). The Smoothed Sunspot Number (SSN) for September is
46 (new scale), 32 (old scale). September's sunspot numbers are
easily the highest of the new solar cycle thus far.
"And the good news doesn't stop there. On September 14 Scott
MacIntosh from the National Center for Atmospheric Research
announced that he expects the termination event concluding Solar
Cycle 24 is imminent and a rapid run-up in solar activity to
commence in mid-November. Solar minimum was recorded in November
2019, the last SWPC numbered SC24 sunspot was observed in July 2020,
the last un-numbered SC24 active region was observed on August 14,
2021. It appears that Solar Cycle 24 is over.

"73 and Best DX!"

More sunspot coverage from local newspapers:

And this:

Bil Paul, KD6JUI from Dixon, California, who operates from his
kayak, sent this on September 27:

"You're probably getting reports of a great opening to Europe
Sunday, but here's my story:

"I was operating from my kayak with 10 watts and a home-brew small
loop on Sunday around noon when I allowed the wind to orient the
boat and the antenna in the direction it chose. That was toward the
northeast from CA, fortunate because Europe was coming in like
gangbusters. Operating SSB, I first contacted IK7YTT in Italy on
17m, followed by Spain and Hungary on 20m. They all had a little
trouble making out my callsign but make it out they did. My location
was Lake Berryessa in Napa County, California.

"This opening certainly provides hope for further such openings
during the coming solar cycle peak. I'm not too surprised when I can
contact Japan or Australia from CA, but Europe is something else

The latest from Dr. Tamitha Skov, WX6SWW, with some exciting news:

If you would like to make a comment or have a tip for our readers,
please email the author at, .

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service web page at, For
an explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good
information and tutorials on propagation are at

Instructions for starting or ending email distribution of ARRL
bulletins are at .

Sunspot numbers for September 23 through 29, 2021 were 75, 75, 38,
67, 30, 57, and 74, with a mean of 59.4. 10.7 cm flux was 89.7,
88.4, 88.4, 86.3, 85.3, 88.9, and 101.6, with a mean of 89.8.
Estimated planetary A indices were 11, 8, 7, 3, 7, 10, and 5, with a
mean of 7.3. Middle latitude A index was 10, 6, 7, 2, 6, 9, and 4,
with a mean of 6.3.


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