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The K7RA Solar Update


With the big increase in sunspot numbers and solar flux reported in
last week's Propagation Forecast Bulletin ARLP013, I hoped the trend
would continue, but numbers this week were lower.

Five new sunspot groups emerged, one each day from March 30 through
April 3.

Average daily sunspot numbers went from 147 to 60, and average daily
solar flux declined from 191.9 to 136.9.

Geomagnetic numbers were much quieter. Average daily planetary A
index softened to 7.6 from 25.4.

Predicted solar flux is 115 on April 5-8, 120 on April 9-10, 125 on
April 11, 140 on April 12-13, 150 on April 14-16, 160 on April
17-18, 170 on April 19-24, then 160, 150 and 140 on April 25-27,
then 130 on April 28 through May 4 then 160, 150, and 140 on May
5-10, then 150 on May 11-13.

The predicted flux values this week are much lower than in last
week's forecast for the same period.

Predicted planetary A index is 16 and 10 on April 5-6, 5 on April
7-8, 8 on April 9-10, 5 on April 11-18, 8 and 10 on April 19-20, 8
on April 21-23, 5 on April 24-26, 10 on April 27-28, 8 on April 29,
and 12 on April 30 through May 2, then 8, 5 and 5 on May 3-5, 8 on
May 6-8, and 5 on May 9-15.

The Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - April 4, 2024 from OK1HH:

"The two large and very active sunspot groups, AR3614 and AR3615,
bade us farewell last week by going beyond the western limb of the
solar disk. AR3615 still unleashed two powerful M-class flares and
an X1 flare that ionized the upper part of the Earth's atmosphere
and caused the Dellinger effect (shortwave fade) over the Pacific
Ocean on March 28 (with a maximum at 2053 UTC).

"AR3615 still managed to produce an M9.4-class solar flare on March
30, which was only one percent weaker than an X-class flare. After
that, we expected particles originating from solar radiation to
arrive in the vicinity of Earth, but this did not happen. The
development in the following days was therefore relatively quiet.

"Due to the calming of the geomagnetic field, we expected an
improvement in shortwave propagation. This occurred from 2 April
onwards but was only very slight due to the rapid decrease in solar
activity. After the return of active regions to the solar disk, we
expect an improvement in propagation, especially in the third decade
of April."

(I think he refers to a decade as a ten day period, so this would be
the last ten days of April).

Angel Santana, WP3GW, sent an email about last week's contest:

"WPX for me was pretty good even though I did not reach my goal.
There were openings toward Europe during Saturday midnight on 20

"Now on Sunday at midday, I noticed a reduction of stations on 10
meters, just like 2 weeks ago, but there were many strong stations
from South America and an hour later back to normal. My friend Jose,
KP4JRS (who operated as NP3YL) noticed this over the two days on 10

"Also noticed when a big contest is on the air, the bands tend to be
almost 'noiseless.'

"Not sure if because the SFI has gone down but today Thursday at
1500 UTC there is much noise on the bands. Hope the weekend fares

WX2R reminds us that coming up on Monday, April 8 is the HamSCI
Solar Eclipse QSO Party:

"Join with thousands of your fellow amateurs as part of the largest
crowd-sourced event for ham radio scientific exploration ever! The
SEQP is part of 'The Festivals of Eclipse Ionospheric Science' and
is for learning more about how the ionosphere works. Use any mode,
any band for all or part of the day!

"Participation can be from everywhere - you need not be near the
path of the eclipse to contribute valuable data by participating.

"Are you a contester? For details on the SEQP contest and rules go
to Don't forget to send in your log.

"For the Gladstone Signal Spotting Challenge using CW, WSPR and
FST4W modes, go to

"If you're an SWL or AM DX'er, there is the 'Medium Wave Recording
Event' for you as well. Go to

"Or just get on the air and help provide the data to better
understand the ionosphere.  Monday, 8 April 2024. Get on the air!
1400-2400 UTC.

"Do it for science! Any band/any mode except 60, 30, 17, and 12

From Forbes Magazine, an eclipse guide:

A DailyMotion video of a long duration flare, but no date given:

Chip, N2YO, sent this email last week.

"Thanks for your excellent ARRL propagation bulletins!

"I also am running a weekly propagation bulletin for more than 20
years (in Romanian language). The bulletin is available on the web,
distributed online by email, and read during the 'Info DX' QTC on
80m each Thursday in Romania.

"All bulletins are available here:

"On the first of each month I update a page of propagation charts in
certain directions, centered on YO:

"I also run a YO DX Cluster which is powered by a DX Spider server
hosted by a Raspberry Pi in my basement that feeds a web page:


"In fact, I run the whole website, which is the most
popular YO ham radio resource on internet. This year the website
will have the 20th anniversary."

Recent 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.

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 March 28 through April 3 2024 were 101, 79, 60,
50, 50, 35, and 45, with a mean of 60. 10.7 cm flux was 172.7,
167.3, 139.6, 133.6, 120.4, 112.8, and 111.7, with a mean of 136.9.
Estimated planetary A indices were 7, 6, 5, 9, 11, 8, and 7, with a
mean of 7.6. Middle latitude A index was 6, 4, 4, 8, 9, 7, and 10,
with a mean of 6.9.




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