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ARRL Propagation Bulletin ARLP026 (2023)

ARLP026 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 26  ARLP026
From Tad Cook, K7RA
Seattle, WA  June 30, 2023
To all radio amateurs 

ARLP026 Propagation de K7RA

Space Weather News sent this alert on June 29:

"BIG SUNSPOT ALERT: One of the biggest sunspots in years is directly
facing Earth. AR3354 is 10 times wider than Earth and about 1/3rd
the size of the historical Carrington sunspot. It's so big,
observers in Europe and North America are seeing it naked eye
through the smoke of Canadian wildfires. Earth-directed flares are
likely in the days ahead."

See for continuing coverage.

Conditions were favorable over the Field Day weekend, with the
exception of a brief period when the planetary K index rose to 5 on
Saturday night. This is mentioned in the commentary by OK1HH which

There were five new sunspot groups on June 23, two more on June 24,
another on June 26 and another on June 27.

Average daily sunspot numbers were up, and solar flux was down.

Average daily sunspot number rose from 143 to 170, and average daily
solar flux declined slightly from 165.4 to 160.3.

This is unexpected, because we normally see these values track

Predicted solar flux is 150 on June 30 through July 5, 155 on July
6, 135 on July 7-8, then 145, 155, 160, 165 and 170 on July 9-13,
175 on July 14-18, 170 on July 19-21, then 160, 150, 145, 145, 140
and 135 on July 22-27, then 130 on July 28 through August 1, 135 on
August 2-4, then 145, 155, and 165 on August 5-7. Flux values may
continue to rise to a peak of 175 before mid-August.

Predicted planetary A index is 8, 15 and 10 on June 30 through July
2, 5 on July 3-7, 12 and 8 on July 8-9, 5 on July 10-11, then a
stormy 20 and 30 on July 12-13, 8 on July 14-23, 12 on July 24-25, 8
on July 26-27, 12 on July 28-29, 8 on July 30, 5 on July 31 through
August 3, 12 and 8 on August 4-5, 5 on August 6-7, then 20 and 30
again on August 8-9. Note that recurring stormy conditions are
predicted at one solar rotation, which is about 27.5 days, following
the July 12-13 prediction.

The above predictions are from forecasters Thompson and Kiser at the
USAF space weather group.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere June 30 to July 06, 2023 from F.K. Janda OK1HH.

"In the solar X-ray field during June we could observe the most
significant solar flare so far: X1 in the active region AR3341. It
happened on June 20 at 1709 UTC near the southeastern limb of the
solar disk. In the region where the Sun was high, it caused the
Dellinger Effect, .

"The same sunspot group was also the source of the M4.8 flare two
days later. It ejected a CME, but not toward Earth.

"Nevertheless, its passage close to Earth probably caused an
increase in geomagnetic activity on the evening of 24 June.
Theoretically, it could also have been a CME from the X1 eruption of
20 June.

"On June 26, we were surprised by sunspot group AR3354 just above
the solar equator and east of the central meridian. It did not exist
the day prior. Over the next two days its area grew to ten times the
size of the Earth, making it easily observable by the naked eye.

"Significantly, its magnetic configuration changed to
beta-gamma-delta, which is enough energy for powerful solar flares.

"The geomagnetic field has been quiet to unsettled so far.

"AR3354 will be pointed directly toward Earth in the next few days,
so it looks like the next disturbance could begin on July 1. And of
course, a possible large flare could cause a Dellinger Effect
throughout the whole HF spectrum."

Pat, W5THT wrote:

"I have been an active ham since 1956 and on the Mississippi coast
since 1971. This year has strengthened my belief in an old
"There is/was a dome of high pressure that moved from over Texas to
now over me. Before it moved east, I was able to take part in the 6
meter propagation to Europe.

"Since it moved over me, the DX Maps page shows a gap in the DX
propagation from northern Florida to central Louisiana.  This is not
the first time I have seen it happen, but the new generation of TV
weather persons presented a picture of the dome of high pressure
that coincided with my propagation observations. Suspicions

"Years ago, on 2 meters I noticed that propagation followed weather
fronts up the east coast. Thanks for reading this and perhaps
someone younger than me has already done the research."

Jon Jones, N0JK wrote:

"Wow -- a surprise opening on 6 meter FT8 to Brazil June 25!

"A CME impact at 1900 UTC may have boosted the TEP MUF Sunday
afternoon. That and some help with sporadic-E -- opening to Brazil
on 6 meters from North America during the summer.

"Had been out with our dog. Saw WQ0P PSK flags for PY2XB. Turned on
radio at home with dipole. PY2XB was loud. Really loud. Also copied
PY5CC. He spotted me as well, but no QSO. PY2XB in for almost half
an hour. Like a pipeline. Saw him work a few 5s and 0s. KC0CF worked
CE2SV. With higher solar activity, the TEP zone still works even in
our summer. This mode works for D2UY (Angola), 3B9FR (Rodrigues
Island in Indian Ocean), and ZL."

An article on Solar Cycle 25 peak and nice images:

Understanding Space Weather: A Glossary of Terms:

"Astro Bob" on that big sunspot:

Frequent contributor David Moore shared this fascinating article
comparing the current big sunspot with the one that launched the
infamous Carrington Event 164 years ago.

Another Solar Cycle article:

Yet another Carrington Event article:

Article about Solar max:

A Houston Chronicle article on solar max:

Flares and how they are measured:

A video from Dr. Tamitha Skov, WX6SWW, from last week:

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 June 22 through 28, 2023 were 176, 194, 200,
180, 158, 141, and 141, with a mean of 170. 10.7 cm flux was 173.2,
169.7, 160.8, 154.8, 157.7, 151.2, and 154.9, with a mean of 160.3.
Estimated planetary A indices were 8, 9, 16, 15, 11, 8, and 8, with
a mean of 10.7. Middle latitude A index was 8, 9, 16, 10, 11, 7, and
8, with a mean of 9.9.


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