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ARRL Propagation Bulletin ARLP054 (2006)

ARLP054 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 54  ARLP054
From Tad Cook, K7RA
Seattle, WA  December 29, 2006
To all radio amateurs 

ARLP054 Propagation de K7RA

More zero sunspot days are finishing out the month, which seems
appropriate as we descend near the bottom of Solar Cycle 23. There
were seven continuous spotless days from December 18-24, then three
days of sunspot numbers 31, 25 and 23, and Thursday, December 28 was
another zero sunspot day. Solar flux numbers, which are not a count
of sunspots, but instead a reading of daily 2.8 GHz energy from the
sun, still seem high for the bottom of the cycle. We should see
extended periods with a daily solar flux around 67 toward the bottom
of the sunspot cycle. Instead, this week the average solar flux was
around 74. If we look back to the four bulletins published a decade
ago in October 1996, we see average solar flux of 69.9, 68.6, 67.9,
and 69.7.

This is the last bulletin of 2006. Next week we will have all the
data to observe the average sunspot numbers for the year, and
compare them with previous years. With just a few more days left in
2006, it looks like annual average daily sunspot numbers will be
running nearly 23 points lower than 2005, which is down 46 percent,
and the annual average of daily solar flux will be around 12 points,
or 13 percent lower.

For the last days of 2006 into New Year's Day we should see quiet
conditions, and no geomagnetic storms or days with active conditions
are expected until January 2-3, with a predicted planetary A index
of 25. Geophysical Institute Prague predicts quiet conditions for
December 29-31, quiet to unsettled January 1, active conditions
January 2, unsettled to active January 3, and unsettled January 4.
Solar flux is expected to rise daily through the week, with
predicted values for December 29 through January 4 of 75, 80, 85,
90, 95, 100 and 100. Sunspot numbers should also rise over the next

Expect good conditions for Straight Key Night, the annual casual
operating activity running from 0000z through 2400z on January 1,
which of course covers all of New Year's Eve here in North America.
For details, see and the rules for
this popular activity at,

On the Saturday before Straight Key Night (actually tomorrow,
December 30) AM operators using primarily big tube type equipment
will have their own operating activity, the Heavy Metal Rally, on
160, 80 and 40 meters. See for details,
and for an interesting article from a few years ago see,

Predictions for the magnitude of solar cycle 24, which should begin
in 2007 and peak around five years from now, seem to vary all over
the place. Some predict one of the strongest most intense cycles in
history, while others see a very weak cycle. An article in Space
News (a print publication) reported this on December 18, and Doc
Silvern, K6RXU of Clarkdale, Arizona passed it on to us. The Space
News web site is, but the full text
of the article cannot be seen online.

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

For more information concerning radio propagation, see the ARRL
Technical Information Service at, For a detailed
explanation of the numbers used in this bulletin see, An archive of past
propagation bulletins is at, .
Monthly propagation charts between four USA regions and twelve
overseas locations are at,

Sunspot numbers for December 21 through 27 were 0, 0, 0, 0, 31, 25
and 23 with a mean of 11.3. 10.7 cm flux was 72.3, 73.2, 72.7, 73.5,
76.4, 75, and 73.3, with a mean of 73.8. Estimated planetary A
indices were 14, 14, 15, 10, 6, 3 and 2 with a mean of 9.1.
Estimated mid-latitude A indices were 9, 10, 10, 7, 4, 3 and 2, with
a mean of 6.4.


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