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ARRL Propagation Bulletin ARLP051 (2021)

ARLP051 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 51  ARLP051
From Tad Cook, K7RA
Seattle, WA  December 17, 2021
To all radio amateurs 

ARLP051 Propagation de K7RA

Sunspots disappeared over four days, December 8-11. Average daily
sunspot numbers and solar flux hardly changed at all, with sunspots
at 24.4 during the current reporting week (December 9-15) compared
to 24.6 last week, and average daily solar flux shifting from 82.6
to 82.9.

By Wednesday solar flux rose to 102.5. But sunspots have come back
dramatically over the past few days, with the daily sunspot number
hitting 127 on Thursday, December 16. On that same day, the noon
10.7 cm solar flux reading at the Penticton observatory was 117.9
and it reached 121.5 at the 2200 UTC reading.

Geomagnetic activity was quiet. Average daily planetary A index
changed from 7.6 to 5, and average daily middle latitude A index
from 5.3 to 3.9.

One new sunspot group emerged on December 12, then two the following
day, two more on December 15 and another two on December 16.

Predicted solar flux over the next month looks very good for this
week, at 118 on December 17-21, 115 and 110 on December 22-23, 82 on
December 24-27, 80 on December 28, 78 on December 29, 2021 through
January 3, 2022, then 80 on January 4-10, 82 on January 11, and 84
on January 12-17. The predicted flux values then drop below 80 after
January 24.

Predicted planetary A index is 8 on December 17, 5 on December
18-19, then 8, 16, 12 and 8 on December 20-23, 5 on December 24-26,
then 15, 18 and 12 on December 27-29, 8 on December 30, 2021 through
January 1, 2022, 5 on January 2-8, then 8 and 5 on January 9-10,
then 12, 10, 10, and 8 on January 11-14, 5 on January 15-22, then
15, 18 and 12 on January 23-25, and 8 on January 26-28.

Unfortunately, propagation was poor last weekend during the annual
ARRL 10 Meter Contest, not surprising with no sunspots on the two
days prior to the contest and non through the weekend. On Friday
night I heard no signals (with a modest dipole antenna), so I called
CQ using CW just above 28 MHz, and worked one local station, only 8
miles away. I worked a few stations on Sunday across North America,
and heard many TEP signals from South America.

Don't miss "Understanding an Ionosonde to Understand the Ionosphere"
by propagation expert KL7AJ in January 2022 QST, currently available

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - December 16, 2021 from F.K. Janda, OK1HH.

"Solar activity has risen a little more and faster in recent days
than we expected. After several smaller eruptions, the probability
of an M-class solar flare increased. Although Solar Cycle 25 is
still closer to the minimum, we can expect its maximum in 3 to 4
years to be higher than usually predicted. The last rise in solar
activity is not long (in recent days only), after that a decline can
be expected again in the last week of December.

"Although most of the active areas are located south of the solar
equator and not too far from the coronal holes, we still expect only
a slight increase in geomagnetic activity at the beginning of the
third week of December.

"The Earth's ionosphere reacted significantly to the last rise of
solar radiation by the rise of MUF. However, the hitherto stable
development will be replaced by fluctuations and deformations of the
daily course - which will happen immediately, probably at the
beginning of the third week of December. This will be followed by a
relatively significant decrease in MUF, both day and night. The
decline of MUF by night will be significant if the onset of the
increase in geomagnetic activity will be up during the night."

Here is a geomagnetic activity summary from Tomas Bayer, RWC Prague
Institute of Geophysics of the ASCR, Prague Department of
Geomagnetism, Budkov observatory, preceded by a geomagnetic activity
forecast for the period December 17-23, 2021:

"Quiet: December 17-18, 22-23
Unsettled: December 18-22
Active: December 18-19
Minor storm: unlikely about December 19
Major storm: 0
Severe storm: 0

"We expect geomagnetic activity enhancement about December 18-19. We
expect an unsettled to active episode, storming defect is less
probable.  Till this event, and also at the end of current forecast
period, we expect at most quiet to unsettled conditions."

Max White, M0VNG sent this from the European Space Agency:

Dr. Tamitha Skov, WX6SWW has more of her continuing space weather

I received many emails correcting the info I gave last week on the
Fred Fish Memorial Award.  This sums it up best:

If you would like to make a comment or have a tip for our readers,
please email the author at, .

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

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

Sunspot numbers for December 9 through 15, 2021 were 0, 0, 0, 12,
40, 40, and 79, with a mean of 24.4. 10.7 cm flux was 76.7, 75.7,
76.2, 79.9, 80.6, 88.9, and 102.5, with a mean of 82.9. Estimated
planetary A indices were 3, 4, 5, 3, 6, 5, and 9, with a mean of 5.
Middle latitude A index was 2, 2, 3, 2, 6, 4, and 8, with a mean of


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