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ARRL Propagation Bulletin ARLP008 (2024)

ARLP008 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 8  ARLP008
From Tad Cook, K7RA
Seattle, WA  February 23, 2024
To all radio amateurs 

ARLP008 Propagation de K7RA


"A solar filament has erupted from the northwest solar quadrant and
a component of the predominately westward associated CME is expected
to arrive at the Earth during the second half of 24-Feb. G1
conditions, with the chance of G2 periods are possible during the
second half of 24-Feb and first half of 25-Feb. Modeling shows the
bulk of the CME missing the Earth.

EJECTION FROM 24-25 FEBRUARY 2024." wrote on February 22:

"TWO MAJOR SOLAR FLARES: Giant sunspot AR3590 just unleashed two
major X-class solar flares. The double blast approximately coincided
with a widely reported outage of cell phone service; however,
experts agree that the flares were probably not responsible. More
flares are in the offing. The sunspot has an unstable 'delta-class'
magnetic field, and it is turning toward Earth."

Sunspot numbers and solar flux values dropped over the past week,
with average daily sunspot numbers down from 134.6 to 84.4 and
average daily solar flux dropping from 190 to 164.

Geomagnetic conditions were very quiet. Planetary A index declined
from the low value of 7.4 to 4.4, and middle latitude A index from
6.1 to 3.5.

Only four new sunspot groups appeared, three on February 15 and one
on February 18. says all their content is written by humans, with
no Artificial Intelligence at all.

I decided to ask an AI bot when Solar Cycle 25 will peak:

From Gemini AI bot:

"There are two main perspectives on when Solar Cycle 25 will reach
its maximum:

"Original prediction:

"An expert panel convened by NOAA, NASA, and ISES in 2019 predicted
a peak in July 2025 with a maximum sunspot number of 115.

"This prediction assumed a similar strength to the weak Solar Cycle

"Revised prediction:

"In October 2023, NOAA's Space Weather Prediction Center (SWPC)
released a revised prediction based on observed activity. This new
prediction suggests a faster rise and higher peak, likely between
January and October 2024, with a sunspot number between 137 and 173.

"However, it's important to note that the timing could still fall
within the broad error range of November 2024 to March 2026.

"So, the answer depends on which prediction you consider:

"Original prediction: July 2025

"Revised prediction: Between January and October 2024 (more likely
than July 2025).

"It's important to stay updated on the latest information as
scientists continue to monitor the Sun's activity. You can find more
details and updates on the NOAA Space Weather Prediction Center



I have bookmarked that last link.

ISES stands for the International Space Environment Service.

Here is a revised outlook for the next month, from USAF via NOAA.

Predicted solar flux is 175 on February 23, 180 on February 24-29,
then 160 and 165 on March 1-2, 170 on March 3-9, 165 on March 10-16,
then 162, 160, and 165 on March 17-19, 170 on March 20-21, 172 on
March 22-23, 165 on March 24-26, and 155, 160, and 165 on March
27-29, and 170 on March 30 into the first week in April.

Predicted planetary A index is 6, 5, 20 and 10 on February 23-26,
and 5 on February 27 through March 23, 8 and 7 on March 24-25, and 5
on March 26 through the first week in April.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - February 23-29, 2024 from F.K. Janda, OK1HH:

"During the last seven days, based on helioseismological
observations we first expected the rise of a larger active region at
the northeastern limb of the solar disk.

"Meanwhile, gradually most of the sunspot groups on its western half
have faded, whereby the solar flux has dropped to 152.

"The larger active region came out, was designated AR3590, and is
large enough to observe with the naked eye (in relation to the area
over 700 millionths of the solar disk), for example, using a solar
eclipse filter. However, its beta-gamma magnetic configuration was
not conducive to larger flares. All the more surprising were two
successive X-class flares: X1.8 on 21 February with a maximum at
2307 UT and X.1.7 on 22 February with a maximum at 0632 UT. However,
they were short-lived and not accompanied by CMEs. During the first
of these, shortwave propagation subsided, particularly in the
western USA and the Pacific (the Dellinger effect).

"Expect an increase in solar X-ray and ultraviolet radiation in the
coming days and mostly geomagnetically quiet conditions. As Spring
approaches, shortwave propagation will be mostly above average or
even better."

K7BTW posted this to the Western Washington DX Club email list on
February 20:

"Fantastic band conditions.

"If you're not taking advantage of these band conditions, you are
missing a lot. On 20 meters FT8 in the last few minutes around 8pm
(0400 UTC) I worked Middle East stations in Lebanon, Jordan, Saudi
Arabia, and Qatar, plus several UN and many Russians. Over the pole
conditions are incredible.

"Take advantage of the sunspot cycle.  We know what it will be like
in 5 years!"

Jeff, N8II wrote on February 16:

"If we are at the peak, I would think this is a poor cycle.

"Not long ago the flux dropped below 130 briefly.

"10 meter conditions are excellent now with much better conditions
to East Asia in the evening than the first 3 weeks of January.

"Today at 2400 UTC 10 meters was open well to Taiwan working BX5AA
and also a BD4 around 0030 UTC. Japanese signals were excellent
until just before 0100 UTC. I heard 8R7X in Guyana running many
Japanese until 0100 UTC on 10 CW."

Here in Seattle where I (K7RA) live we have always had a pipeline to
Japan, which at times can seem overwhelming.

Reader David Moore sent this article from the European Space Agency:

Articles about powerful Solar Flares:

Geo News article about the Solar max:

Big sunspot AR3590 visible to the eye:

The latest report 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.

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 .

Also, check this QST article about Solar Indices:

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

Sunspot numbers for February 15 through 21 2024 were 151, 97, 100,
84, 64, 50, and 45, with a mean of 84.4. 10.7 cm flux was 178.3,
168.8, 169.9, 156.5, 152.1, 152.6, and 169.9, with a mean of 164.
Estimated planetary A indices were 4, 4, 4, 6, 3, 6, and 4, with a
mean of 4.4. Middle latitude A index was 3, 3, 4, 4, 1, 5, and 3,
with a mean of 3.3.


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