SB PROP @ ARL $ARLP012
ARLP012 Propagation de K7RA
ZCZC AP12
QST de W1AW
Propagation Forecast Bulletin 12 ARLP012
From Tad Cook, K7RA
Seattle, WA March 22, 2024
To all radio amateurs
SB PROP ARL ARLP012
ARLP012 Propagation de K7RA
Over March 14-20, new sunspot groups emerged every day except March
19. March 18 had two, and each of the other days saw one new sunspot
group.
It is now Spring in the Northern Hemisphere which is favorable to HF
conditions, and solar and geomagnetic numbers both show improvement.
Average daily sunspot numbers rose from 82.3 to 94.3, and average
daily solar flux jumped from 130.4 to 153.3.
Geomagnetic indicators were very quiet, with the average daily
planetary A index dropping from 8.9 to 5.9, and middle latitude
numbers from 7 to 5.
Here is the outlook for the next month.
Predicted solar flux is 180 and 178 on March 22-23, 174 on March
24-25, then 176 on March 26-27, 178 on March 28, 165 on March 29-30,
160 on March 31, 155 on April 1-3, then 158 on April 4, 160 on April
5-6, then 162, 155, 150, and 145 on April 7-10, 148 on April 11-12,
then 152, 155, 160, 162, 165 and 160 on April 13-18, then 155 on
April 19-20, 152 on April 21, 160 on April 22-23, then 162, 165, 165
and 160 on April 24-27, and 155 on April 28-30.
Predicted planetary A index is 12, 5, 16, 18 and 8 on March 22-26,
then 5, 5 and 8 on March 27-29, 5 on March 30 through April 2, then
15, 12 and 12 on April 3-5, 5 on April 6-8, 8 on April 9-11, then 5
on April 12-23, 10 on April 24-25, and 5 on April 26-29.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - March 21, 2024, from F.K. Janda, OK1HH:
"Solar activity on average continues to increase toward the Solar
Cycle 25 maximum. This included a shower of protons that came from
the admittedly smaller in X-ray intensity but primarily long-lived
flare on the morning hours UTC of March 15. The particle density
peaked a day later when the proton event reached S1. High polar cap
absorption of radio waves was recorded at the same time.
"The geomagnetic field remains mostly calm, with the occurrence of
short active intervals. An increase in geomagnetic activity was
expected after the eruption of 17 March. A partial CME halo was
observed and ejected particles were expected in the vicinity of the
Earth first on 20 March, then on the evening of 20 March, and then
on the morning of 21 March. The result was an increase in MUF
already in the forenoon UTC. An increase in the Earth's magnetic
field activity occurred in the afternoon.
"The new sunspot group AR3615, which emerged in the southeast of the
solar disk, although not yet large, has a complex magnetic
structure. This configuration increases the probability of magnetic
reconnection during a solar flare. Especially if an X-class solar
flare occurs, the probability of CME will increase."
Angel Santana, WP3GW wrote about conditions on March 16 in an email:
"With much expectation worked the Russian DX contest on SSB, but
then noticed rough conditions, so bad that after 1600 UTC signals
were gone, not seen on my radio. After 1730 UTC saw them come back
but conditions were still bad.
"Next day did the BARTG RTTY contest after 1430 UTC and fared
better.
"Did it have to do with one of the six sunspots last week? Hope prop
is good in a week from now."
I replied that according to Spaceweather.com, departing sunspot
AR3599 blasted protons toward Earth on March 14, causing a polar cap
absorption event on March 16. The ionizing effect of the protons
absorbed radio signals inside the arctic circle.
Nasa Space Flight article about VLA detection of radiation above
sunspots:
https://bit.ly/4cDDref
Article about Radio Blackout:
https://bit.ly/3ILT6KH
From Dr. Tamitha Skov, WX6SWW:
"Dear Tad,
"Recently our Sun gave us a surprise when a solar storm we thought
would be a glancing blow, actually hit us pretty hard. That was back
on March 3rd and some gorgeous aurora shows were seen in Tasmania
and Australia (see my forecast from that week for some amazing
pictures: https://youtu.be/2nWLAYL01FA).
"Here we are several weeks later with yet another glancing blow set
to hit us midday March 20th. The official forecast is calling for a
weak impact, but our recent experience has left me wondering: Are we
are going to make the same mistake twice?
"These are the kinds of dilemmas that make space weather such a
tough field today. Compared to terrestrial weather, there are so
many things we simply cannot foresee.
"Turning to the forecast, big flare activity is beginning again
thanks to old Region 3590 rotating back into view along with some
new players as well. Amateur radio bands are getting noisier and
radio blackouts are resuming on the daylight side of Earth. Of
course, the big story is the solar storm coming towards us. Will it
be relatively mild at mid-latitudes, as the predictions suggest?
This time, I'm not so sure. Either way, I will remain on the
lookout.
"Cheers, Tamitha."
Here is her latest video report:
https://youtu.be/O6vZDFaBfrc
Send your tips, reports, observations, questions, and comments to
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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/ .
Also, check this QST article about Solar Indices:
https://bit.ly/3Rc8Njt
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .
Sunspot numbers for March 14 through 20 2024 were 88, 49, 67, 86,
127, 123, and 120, with a mean of 94.3. 10.7 cm flux was 127.1, 129,
144.1, 151.3, 177.4, 168.9, and 175.5, with a mean of 153.3.
Estimated planetary A indices were 8, 8, 3, 3, 6, 9, and 4, with a
mean of 5.9. Middle latitude A index was 7, 8, 3, 2, 5, 7, and 3,
with a mean of 5.
NNNN
/EX
