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ARRL Propagation Bulletin ARLP029 (2023)

ARLP029 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 21, 2023
To all radio amateurs 

ARLP029 Propagation de K7RA

Average daily sunspot numbers declined, but average daily solar flux
increased.  Sunspot averages were 181.9 last week, and 130.6 this
week.  Average daily solar flux increased from 179.4 to 190.5.

Two new sunspot groups emerged on July 14, three more on July 17 and
another two on July 19.

Average daily planetary and middle latitude A index were both 12.9
this week, rising from 8.6 and 8.1.

Predicted solar flux is 185 on July 21-23, then 180, 178, 175 and
170 on July 24-27, 165 on July 28-29, 170 on July 30-31, 165 on
August 1-4, then 170, 175, 175 and 170 on August 5-8, 165 on August
9-11, 170 on August 12, 175 on August 13-14, and 170 on August
15-19, 160 on August 20-23, 165 on August 24-25, then 170 on August
26-27 and 165 on August 28-31.

Predicted planetary A index is 20, 12, 8, 12 and 10 on July 21-25, 5
on July 26 through August 2, then 10 and 8 on August 3-4, 5 on
August 5-14, then 12, 8 and 8 on August 15-17, and 5 on August

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere for July 20, 2023 from OK1HH.

"We've seen another seven days of mostly moderate solar activity,
with almost daily eruptions of moderate magnitude on the Sun.  Some
of these have been the source of CMEs.  If the Earth has been
affected by them, a geomagnetic disturbance followed, with a drop in
MUF and a worsening of HF propagation in the process.

As predicted, the expected CME hit the Earth's magnetic field on the
afternoon of 14 July (as part of the Bastille Day celebrations, but
not nearly as strongly as in 2000).

Another CME left the Sun on 14 July, and yet another on July 15.
Because the cloud of later ejected solar plasma was faster, it
cannibalized the previous CME.  Together, they hit the Earth on July

But by then AR3363 had already produced a significant long-lasting
M6-class solar flare, and energetic protons accelerated by this
flare reached the Earth and caused a radiation storm.  Although MUFs
were quite high, HF conditions were adversely affected by frequent
occurrences of attenuation.

Another CME hit the Earth on 20 July, registered by the Earth's
magnetic field at 1708 UTC.

Further developments were predicted up to G1 to G2 class geomagnetic
storms, with a small probability also of G3, but by then this report
will have been completed and sent out.

Finally, just a little note on the consequences of global change: it
has been manifested in the last eleven-year cycles, in the Earth's
troposphere it is the result of warming, but in the ionosphere it is
rather the opposite.  It has been the subject of a number of
scientific papers in recent years.

It is crucial for us, for amateur radio practice, that the current
MUFs are lower than those calculated from sunspot counts for most of
the twentieth century.  Therefore, we should input Ri (or solar flux
SFU) into forecast programs lower than what is currently measured
and published.

F.K. Janda, A.R.S. OK1HH "

News from N8II in West Virginia.

"The bands are in much better shape than most hams realize; activity
levels are normally quite low this summer.  In the IARU contest I
observed 15M open to Europe through 0300 UTC and I had QSOs with
Indonesia, China, Nepal, Japan, Central/Western Siberia, Kazakhstan,
and the Philippines in the 2300-0300 UTC period.

I copied GR2HQ (Great Britain HQ station) on 10M CW at 0140 UTC.  At
1100 UTC on 15M EU and Central/West Asia were very loud and I
started running a pile up on CW.

The Far East was also in on 15M around 1400 UTC Saturday when I
worked a loud Japanese station.

During the evening/night EU signals were extremely loud on 20M.  I
also worked a few EU on 10M 1300-1400 UTC Saturday thanks to
Sporadic E and also caught Z30HQ (Macedonia HQ) on 10M CW Sunday
about 1130 UTC.  I worked 697 QSOs concentrating on DX on the high
bands in less than 12 hours with 100 W.

Africa is workable on 10-15M well into our evening as are South
Pacific stations.

Sporadic E this year seems somewhat attenuated, but Es was good from
here and great from the Central/Western USA during the June VHF
contest.  I made about 170 CW/SSB QSOs."

CNN presented a smart piece on the sunspot cycle peaking sooner than

Double peaked flare.

Astronomy club observes sunspots.


Scientific American.

Early peak.

Cannibal eruption.

Great video of eruption.

The latest from Space Weather Woman 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.

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 .

Also, check this article from September, 2002 QST:

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 July 13 through 19, 2023 were 146, 141, 96, 99,
149, 142, and 141, with a mean of 130.6.  10.7 cm flux was 202.9,
180.6, 178.5, 184.3, 180, 218.5, and 188.9, with a mean of 190.5.
Estimated planetary A indices were 7, 20, 8, 10, 24, 16, and 5, with
a mean of 12.9.  Middle latitude A index was 9, 17, 9, 13, 19, 16,
and 7, with a mean of 12.9.


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