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ARRL Propagation Bulletin ARLP050 (2021)

ARLP050 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 50  ARLP050
From Tad Cook, K7RA
Seattle, WA  December 10, 2021
To all radio amateurs 

ARLP050 Propagation de K7RA

One new sunspot group appeared on December 4, but four days later it
was gone, and on Thursday, December 9 we saw the second day with no

Average daily sunspot number declined from 46.1 to 24.6. Average
daily solar flux went from 90.9 to 82.6.

Predicted solar flux over the next month does not seem promising.
The December 9 forecast shows 77 on December 10, 80 on December
11-14, 82 on December 15, 84 on December 16-17, 85 on December 18,
87 on December 19-22, 86 on December 23-27, 84 on December 28, 82 on
December 29 through January 2, 80 on January 3-5, 82 on January 6-8,
80 on January 9-10, 82 on January 11, 85 on January 12-14 and 87 on
January 15-18.

Predicted planetary A index is 10, 8, 10 and 8 on December 10-13, 8
on December 13-14, 5 on December 14-15, then 10, 8, 12, 10 and 8 on
December 16-20, 5 on December 21-26, then 15, 18 and 12 on December
27-29, 8 on December 30 through January 3, 5 on January 4-5, then
10, 8, 5, 12 and 10 on January 6-10, 5 on January 11-12, then 15,
12, 10 and 8 on January 13-16, and 5 on January 17-22.

From OK1HH:

"Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere, December 9, 2021.

"(Created as a continuation of Earth's magnetic field activity
predictions, published since 1978.)

"The only sunspot group on solar disk No. 2904, in which we observed
three spots (=> R = 13) on December 7, was calm and decayed to
plage. Thus, R = 0 applies since December 8, so we register a
minimum within the quasi-periodic twenty-seven-day fluctuation. At
the same time, the solar wind has weakened, the geomagnetic field
has calmed down and consequently result are the lowest values of
f0F2. However, the decreasing length of sunshine in the Earth's
northern hemisphere also contributes to it.

"In the remaining weeks until the end of the year, we can expect a
gradual rise in solar activity to the level of the end of November,
an irregular alternation of the Earth's magnetic field between quiet
and unsettled, and a gradual rise in daily f0F2 values just slightly
above average.

"F. K. Janda, A.R.S. OK1HH 
Email: ok1hh(at), ok1hh(at)

This weekend is the annual ARRL 10-Meter Contest! Solar flux should
be rising a modest amount during the event. Debris from asteroid
Phaethon could possibly enhance propagation on 10 meters during the
Geminids meteor shower, peaking on December 13. See for contest details.

N0JK reported on Wednesday from Kansas, "The Geminids Meteor shower
is predicted to peak December 13-14. Already meteor rates are
picking up.

"I was able to work NJ0W/R in grid DN82 on 50 MHz meteor scatter
using the MSK144 mode on December 7, at 0330 UTC. Dave, NJ0W made
other meteor scatter contacts as well. DN82 is considered a rare
grid for the FFMA (Fred Fish Memorial Award) on 6 Meters."

The FFMA will be awarded to anyone working all North America grid
squares on 6 meters. So far Fred Fish is the only ham who has done

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 2 through 8, 2021 were 45, 29, 35, 36,
14, 13, and 0, with a mean of 24.6. 10.7 cm flux was 86.6, 85.3,
88.1, 82.7, 80, 78.9, and 76.9, with a mean of 82.6. Estimated
planetary A indices were 10, 8, 9, 9, 7, 5, and 5, with a mean of
7.6. Middle latitude A index was 7, 4, 7, 6, 6, 3, and 4, with a
mean of 5.3.


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