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ARRL Propagation Bulletin ARLP041 (2023)

ARLP041 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 13, 2023
To all radio amateurs 

ARLP041 Propagation de K7RA

The numbers looked better during this reporting week, October 5-11.

Average daily sunspot numbers rose from 128.6 to 144.1, and average
solar flux from 155.6 to 159.1.

Average daily planetary A index went from 9.1 to 7.6, and average
middle latitude A index from 8.9 to 8.3.

For some reason the middle latitude numbers were not available from
Fredericksburg, Virginia so we used the data from Boulder, Colorado.

Nine new sunspot groups emerged this week, with two on October 5,
one on October 7, two on October 8, one on October 9, another on
October 10, and two more on October 11.

HF conditions have been excellent, as the season turns deeper into
Autumn in the Northern Hemisphere. I really notice a difference on
10, 12 and 15 meters.

Predicted solar flux is 156 on October 13, 155 on October 14-16, 152
on October 17-18, then 150, 148, 150 and 152 on October 19-22, 152
on October 23-24, 158 on October 25, 160 on October 26-28, 158 on
October 29-30, 156 on October 31 through November 1, then 155, 156,
156, 158 and 160 on November 2-6, 158 on November 7-8, then 156 on
November 9-10, then 155, 154, 152 and 150 on November 11-14, 148 on
November 15-16, then 150, 152, 154 and 154 on November 17-20.

Predicted planetary A index is 12, 10, 8, 5, 12, 10 and 8 on October
13-19, 5 on October 20-30, 15 and 12 on October 31 through November
1, 5 on November 2-5, then 10, 8, and 10 on November 6-8, 15 on
November 9-10, then 8 on November 11, and 5 on November 12 to the
end of the month.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere October 13-19, 2023, from F.K. Janda, OK1HH:

"Unlike most days in September, the Earth's geomagnetic activity has
finally dropped. Solar activity is high enough that there was a
significant improvement in shortwave propagation on a global scale.

"Around October 7, although there was still a possibility that Earth
would be hit by a CME that left the Sun on October 3, it did not
happen. Whereupon, especially on quiet days in the middle of this
week, the improvement was unmistakable.

"Two or three sunspot groups continue to be observed on the Sun.
They are able to produce up to moderate intensity flares. But the
area of the spots is not large, so we do not expect a CME based on
their magnetic configuration either.

"Thanks to helioseismology, we know of more extensive active regions
on the far side of the Sun. Therefore, it is safe to assume that
solar activity will be elevated for the rest of October. Which of
course brings with it possible increases in solar wind speeds with
higher particle concentrations, but this is not enough to predict a
disturbance, only to vaguely state the possibility of one."

Dan, K7SS wrote:

"Just an FYI to those of us who may know anyone new to HF, and the
fact that 10m seems to be at a fantastic peak of conditions
recently, it would be a great shame for anyone who is new to HF to
miss this peak (or pre-peak?) with 10m so open during the daylight
and well into the evening darkness. Just recall the thrill of DX you
had early on.

"Would like to encourage everyone [in the club] to think about who
they might know that's pretty new and give a gentle prod to get them
on 10m. Even with a minimal antenna and power, the band is
supporting signals around the world right now. This may be our peak,
or perhaps this is a bellwether of things to come and may get even
better, but maybe not.

"If any tech licensee can get on 10m with even a minimal signal, it
will not disappoint. 28300 to 28500 kHz is theirs, and the
playground is full. And no place better to get the DX BUG than by
working some EU with low power and a small wire or vertical antenna.

"You don't want to have to explain in a year or two from now, that
they SHOULD have been on working DX and if not, may have to wait for
another cycle peak in 12-14 years.

"Personally, I'm having the time of my life with EU openings in the
morning around 10AM-12PM local. The THRILL IS BACK. 10m Lives."

An article about a 15,000 year history of extreme solar events:

Commercial space companies approach their first solar maximum:

Korean records from the 14th to 19th centuries reveal sunspot cycle

Safely watch the eclipse with a disco ball. (I do not know if this
is actually safe):

Articles about the "Ring of Fire" solar eclipse:

An article about the Sun's polarity flip:

Video about Sunspot AR3038:

Optimistic outlook on Aurora:

Don't forget the eclipse event this Saturday, October 14:

And at the last minute Thursday night, a new video from Dr. Tamitha
Skov, WX6SWW:

Send your tips, reports, observations, questions and comments to When reporting observations, don't forget to tell us
which mode you were operating.

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

Also, check this article from September, 2002 QST:

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

Sunspot numbers for October 5 through 11, 2023 were 179, 138, 145,
149, 129, 120, and 149, with a mean of 144.1. 10.7 cm flux was
156.1, 155.3, 157.2, 157.1, 165.5, 164.4, and 158, with a mean of
159.1. Estimated planetary A indices were 16, 9, 5, 7, 8, 4, and 4,
with a mean of 7.6. Middle latitude A index was 17, 8, 4, 10, 9, 6,
and 4, with a mean of 8.3.


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