ARRL
Propagation Forecast Bulletin 16 ARLP016
From Tad Cook, K7RA
Seattle, WA April 22, 2022
To all radio amateurs
SB PROP ARL ARLP016
ARLP016 Propagation de K7RA
Solar flares emerged daily over the last reporting week (April
14-20). On April 20 Spaceweather.com reported "Solar Activity is
Intensifying," and that over the past 24 hours there were 19 solar
flares, including six M-class events, and a powerful X2.2 class
flare.
Daily sunspot numbers averaged 64.4, 30 points higher than last
week, and average daily solar flux also rose 30 points from 103.1 to
133.9.
Yesterday, April 21, the huge array of active Earth facing sunspots
pushed the daily sunspot number clear up to 119, high above the
average for the week of 64.4.
Even with all the flares and CMEs, geomagnetic indicators were
lower, with the average planetary A index going from 16.9 to 14.6,
and middle latitude numbers from 12.6 to 10.9.
Predicted solar flux looked moderate, but the outlook improved
between April 20 and the following day, with flux values at 160 on
April 22-29, 125 on April 30, 130 on May 1-4, 125 on May 5, 130 on
May 6-7, 128 on May 8, 130 on May 9-10, 135 on May 11-12, 140 on May
13-14, 135 on May 15, 130 on May 16-18, 135 on May 19, 130 on May
20-21, 135 on May 22, 132 on May 23-25, 125 on May 26-27, and 130 on
May 28-31.
Predicted planetary A index is 5 and 12 on April 22-23, 12 on April
23, 8 on April 24-25, 5 on April 26-28, then 18, 12 and 8 on April
29 through May 1, 5 on May 2-5, then 8, 15, 12 and 8 on May 6-9, 5
on May 10-12, then 8, 10 and 12 on May 13-15, 10 on May 16-17, 8 on
May 18-19, then 12 and 8 on May 20-21, 5 on May 22-25, then 18, 12
and 8 on May 26-28.
This report from OK1HH:
"A week ago, we knew solar activity would rise, but the reality
exceeded expectations. As predicted, a CME hit Earth's magnetic
field on April 14th. Its impact sparked a moderately strong G2-class
geomagnetic storm, which peaked around 1800 UTC. Apparently due to
the further increasing solar radiation, the disturbance was mainly
accompanied by an improvement in the ionospheric propagation of
decameter waves (10 meters!), which also applied to the following
development.
"Activity prevailed in growing hotspots in the northeast quadrant of
the solar disk. In the following days, the activity of the
southwestern areas increased, including the X2.2-class flare on
April 20th at 0357 UTC, when it came from a far side sunspot. And
finally, on April 21st at 0157 UTC a strong M9.6-class solar flare
was detected. The source was the sunspot complex AR2993-94, which is
almost directly facing Earth, so I expect the intensified solar wind
in the coming days to affect the Earth's magnetosphere and
ionosphere."
Solar flares in the news:
https://www.space.com/sun-unleashes-major-easter-solar-flare
Here is an impressive image:
https://skyandtelescope.org/online-gallery/sun-erupting/
Here are more and more solar flares:
https://www.space.com/solar-x-class-flare-april-2022
https://www.space.com/sdo-image-april-20-moderate-flare
Funny thing is, even with all this activity, I am not seeing much of
an effect on geomagnetic indicators:
https://services.swpc.noaa.gov/text/daily-geomagnetic-indices.txt
More solar news can be found here:
https://bit.ly/3jZtEVF
https://interestingengineering.com/sun-flare-five-years
If you would like to make a comment or have a tip for our readers,
please email the author at, k7ra@arrl.net.
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service web page at, http://arrl.org/propagation-of-rf-signals. For
an explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere.
An archive of past propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at http://k9la.us/.
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .
Sunspot numbers for April 14 through 20, 2022 were 37, 35, 78, 74,
79, 68, and 80, with a mean of 64.4. 10.7 cm flux was 103.4, 110.3,
122.4, 134.9, 140.5, 160.1, and 165.5, with a mean of 133.9.
Estimated planetary A indices were 38, 21, 8, 11, 8, 7, and 9, with
a mean of 14.6. Middle latitude A index was 22, 14, 7, 9, 7, 8, and
9, with a mean of 10.9.
NNNN
/EX
