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ARRL Propagation Bulletin ARLP038 (2022)

ARLP038 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 38  ARLP038
From Tad Cook, K7RA
Seattle, WA  September 23, 2022
To all radio amateurs 

ARLP038 Propagation de K7RA

Geomagnetic disturbances were down this week, but so were sunspot
numbers and solar flux.

Average daily sunspot numbers declined from 92.7 to 68, and average
daily solar flux from 141.3 to 134.3.

On September 22 the sunspot number was 99, well above (by 31 points)
the average for the previous seven days, a promising indication. We
hope it may signal a trend.

But Solar Cycle 25 progresses, a bit better than expected. A year
ago, average daily sunspot numbers were about ten points lower, at
58.3, while average solar flux was 87.4, about 47 points lower. Two
years ago there were no sunspots! We still expect an uptrend lasting
until Summer 2025.

Six new sunspot groups appeared this week, the first on September
15, two more on September 19, another on September 20, and two more
on September 21.

Predicted solar flux is 138 on September 23, 130 on September 24-27,
120 and 125 on September 28-29, 122 on September 30 through October
7, then 125, 122 and 120 on October 8-10, 118 on October 11-12, 116
on October 13-15, 138 on October 16, 135 on October 17-18, then 133,
128, 126, 130 and 125 on October 19-23, 120 on October 24-25, and
122 on October 26-29.

Predicted planetary A index is 20 on September 23, 15 on September
24-25, 8 on September 26-28, then 5, 22, 50, 30 and 20 on September
29 through October 3, then 12, 15, 12 and 10 on October 4-7, then 8,
8, 5, and 8 on October 8-11, 5 on October 12-14, then 12, 10, 5, 5,
20, 18 and 12 on October 15-21, and 8 on October 22-26, then 22, 50,
30, 20 and 12, a repeat from the previous solar rotation.

The above predictions were by Dethlesfsen and Ciopasiu at Offut Air
Force Base.

Are sunspots really black?  A report can be found here:

Pleased to report that the 2022 Autumnal Equinox was today, Friday,
September 23 at 0104 UTC. Both northern and southern hemispheres
will be bathed in equal amounts of solar radiation, which is good
for HF propagation.

Frequent contributor David Moore sent this story about a magnetic
mystery solved with the aid of the Solar Orbiter:

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - September 22, 2022 from F.K. Janda, OK1HH.

"The setting sunspot region AR3098 still managed to produce an
impulsive M8-class solar flare on 16 September at 0949 UT. A sudden
ionospheric disturbance (SWF, or Dellinger effect) affected
frequencies below 25 MHz for an hour after the flare.

"On September 17, we expected the high-speed solar wind flow from
the northern coronal hole to produce a G1-class geomagnetic storm,
but we registered it a day later. Whereupon the old region AR3088
appeared on the eastern limb of the solar disk and was given the new
number AR3102. Although it appeared to be in decay, it grew again.

"On September 18, we observed five M-class solar flares in the
setting region of AR3098. However, none of them produced an
earthward CME.

"On September 20, another large group of spots appeared over the
southeastern edge of the Sun, joining the rising and growing AR3105
- which doubled in size the next day.

"On September 21, NOAA predicted a minor G1-class geomagnetic storm
might occur on September 23. A high-speed solar wind stream is
expected to hit the Earth's magnetic field.

"On September 22, we could observe the sunspot group complex
AR3105-3107. The chance of a geoeffective flare should increase in
the coming days as they enter the Earth's impact zone.

"Geomagnetic activity was somewhat lower than expected.

"Shortwave propagation conditions pleasantly surprised us around
September 17. Therefore, we expected them to improve further as the
Autumnal Equinox approached. But it didn't happen.  They remained at
average levels, whereby the explanation for why this happened lies
in the effect of the solar wind on the Earth's ionosphere."

I (K7RA) had more strange pipeline propagation on 10 meters this
week, in which my FT8 signal was only reported by from stations in Florida.

At 2050 UTC yesterday, AI4FR (2509 miles), N2UJZ (2558 miles),
KD8HTS (2582 miles), and WC3W (2609 miles) were the only stations
anywhere receiving my signal. All were less than 100 miles from each
other.  Later PU5CAC (Brazil, 6847 miles) was added to the mix,
along the same arc as the North America stations.

I was not using any directional antenna, just a random length
end-fed indoor wire fed by a 4:1 UnUn and autotuner. Very curious
results, and it happens often. So, for me, the band was dead, except
to a very specific location.

Here is a space weather report from England's Met Office:

On September 22, reported three big
sunspots crossing the solar horizon: AR3105, AR3106 and AR3107.

Here is always a good reference:

NOAA Space Weather Prediction Center:

Solar Dynamics Observatory:

The SOHO site:

Hilarious solar warning out of India, an EOTWAWKI existential

Send your tips, reports, observations, questions, and comments to

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service 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 15 through 21, 2022 were 71, 64, 76,
51, 74, 70, and 70, with a mean of 68. 10.7 cm flux was 139.7,
131.1, 131.5, 136.1, 127.9, 137.2, and 136.9, with a mean of 134.3.
Estimated planetary A indices were 6, 4, 5, 11, 11, 8, and 5, with a
mean of 7.1. Middle latitude A index was 8, 5, 5, 9, 7, 6, and 4,
with a mean of 6.9.


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