QST de W1AW  
Propagation Forecast Bulletin 15  ARLP015
>From Tad Cook, K7RA
Seattle, WA  April 12, 2024
To all radio amateurs 

SB PROP ARL ARLP015
ARLP015 Propagation de K7RA

I did not see last Monday's eclipse, except on television. Here in
the Pacific Northwest, we only got a 20% exposure, and skies were
overcast.

As they moved across the country displaying successive totality, I
noticed the prominences on the edge of the disk. There were always
between one and three little red spots at the edge.

Solar activity over the past reporting week, April 4-10, remains
weak.

Average daily sunspot number rose from 60 to 67.9, but average solar
flux declined from 136.9 to 123.2.

Seven new sunspot groups emerged this week, one on April 4, three on
April 5, another on April 6, one more on April 8, and another on
April 10.

Here is the outlook for the next few weeks, which does not seem
promising. Solar flux peaks at 160 over April 17-18.

Predicted solar flux is 148, 150 and 155 on April 12-14, 158 on
April 15-16, 160 on April 17-18, 140 on April 19-20, 135 on April
21-22, 140 and 145 on April 23-24, 140 on April 25-26, then 135, 125
and 120 on April 27-29, and 125 on April 30 through May 10, then 130
on May 11-12, 135 on May 13-14, and 130 on May 15-18.

Predicted planetary A index is quiet over the next month, starting
with 5, 8, 15, 10 and 8 on April 12-16, 5 on April 17-18, 8 and 10
on April 19-20, 8 on April 21-23, 5 on April 24-27, then 8, 8 and 7
on April 28-30, 10 on May 1-3, 5 on May 4-5, 8 on May 6-8, and 5 on
May 9-15, then 8 and 10 on May 16-17, and 8 on May 18-20.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - April 11, 2024, from F.K. Janda, OK1HH:

'At the end of March, it was still possible to see large sunspot
groups, during the last solar rotation marked as AR3614 and
especially the giant AR3615. We will see them again on the eastern
limb of the solar disk this weekend. This will end a roughly
two-week period of relatively quiet solar activity without major
solar flares.

'The Sun's total X-ray output, which has dropped by almost an order
of magnitude, will increase significantly, which will have a
beneficial effect on shortwave propagation.

'Daily MUF values will gradually increase, while active regions will
be on the eastern half of the solar disk. For that reason, here will
be little probability of major geomagnetic disturbances. Of course,
now that the peak of the 11-year cycle is approaching, events such
as the eruption of solar plasma filaments that could affect the
Earth cannot be ruled out.'

Douglas Barbier, N8ZVT, wrote in an email:

'Why is the solar flux so low, given the number of sunspots?  What
else may be affecting the solar flux?

'This is my first solar maximum as a ham - and at my age, might be
the last. I had always heard stories of how 10m would be open 24
hours a day for voice and working all over the world with low power
SSB.  Sure haven't seen that yet at all.'

I replied:

'That was nearly 70 years ago at the peak of Solar Cycle 19 when 10
meters was open 24/7.

'There has never been a similar solar cycle since the dawn of radio.
It was all AM back then, no SSB.

'Solar flux readings come from an observatory in Penticton, BC:

'https://www.spaceweather.gc.ca/forecast-prevision/solar-solaire/solarflux/sx-5-flux-en.php

'I have not noticed that solar flux was low.

'Because Earth is in an elliptical orbit around the Sun, a variation
in distance affects solar flux.

'That is why you will see adjusted values in the flux readings from
Penticton.

'You can get a graphic view of sunspot numbers and solar flux from
the WA4TTK solar data plotting utility at:

'www.craigcentral.com/sol.asp

'You can update the data automatically using data from this weekly
bulletin.'

Solar cycles explained:

https://www.snexplores.org/article/explainer-solar-cycle

A solar cycle clock:

https://www.nature.com/articles/s41598-024-58960-5

Flares during eclipse:

https://bit.ly/3VRBxk0

Prominences, not flares:

https://bit.ly/49waWMC

Solar Cycles:

https://bit.ly/3PY4F5p

Internet apocalypse due to solar storms:

https://bit.ly/3vBW69C

Dr. Tamitha Skov, WX6SWW, reports during the eclipse:

https://youtu.be/Z16_Uk1vym8

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

For more information concerning shortwave radio propagation, see
www.arrl.org/propagation and the ARRL Technical Information
Service web page at, arrl.org/propagation-of-rf-signals . For
an explanation of numbers used in this bulletin, see
arrl.org/the-sun-the-earth-the-ionosphere .

An archive of past propagation bulletins is at
arrl.org/w1aw-bulletins-archive-propagation . More good
information and tutorials on propagation are at k9la.us/ .

Also, check this QST article about Solar Indices:

https://bit.ly/3Rc8Njt

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

Sunspot numbers for April 4 through 10 2024 were 47, 81, 71, 79, 79,
64, and 54, with a mean of 67.9. 10.7 cm flux was 113.7, 120.5,
122.9, 124.6, 124.8, 124.4, and 131.2, with a mean of 123.2.
Estimated planetary A indices were 12, 12, 10, 6, 8, 11, and 8, with
a mean of 9.6. Middle latitude A index was 33, 10, 8, 5, 8, 10, and
7, with a mean of 11.6.