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ARRL Propagation Bulletin ARLP007 (2014)

ARLP007 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 7  ARLP007
From Tad Cook, K7RA
Seattle, WA  February 14, 2014
To all radio amateurs 

ARLP007 Propagation de K7RA

There seemed to be a disconnect between daily sunspot numbers and
solar flux over the past reporting week (February 6-12), with the
average daily sunspot number rising 28 points to 184.3, and average
daily solar flux declining 8.5 points to 171.9. Perhaps this
reflects the general weakness in the energy and magnetic complexity
of recent sunspots. Many days we see a substantial number of
sunspots, but they don't produce much activity.

We did see unsettled geomagnetic conditions though on February 8
when the planetary A index reached 23, caused by a CME the day

At 2351 UTC on February 12, the Australian Space Forecast Centre
released this geomagnetic warning: "INCREASED GEOMAGNETIC ACTIVITY
They predict a minor geomagnetic storm on Saturday, February 15. Too
bad that is the first day of the ARRL International CW DX Contest.

The latest forecast from NOAA/USAF has planetary A index at 25 on
February 14, 40 on February 15, 18 on February 16, 12 on February
17, 5 on February 18-24, 8 on February 25, 5 on February 26 through
March 1, 12 on March 2, 5 on March 3-6, and 8 on March 7-9, before
dropping back to 5 until March 16, when it rises to 8 on March

Predicted solar flux values are 165 on February 14, 160 on February
15-17, then 155, 145 and 140 on February 18-20, 145 on February
20-21, then 150, 160, 170, 180, 185, 190 and 200 on February 23
through March 1, then 195, 200, 205 and 210 on March 2-5, before
declining to a low of 130 on March 14, then rising to 200 on March

OK1HH sees quiet to active geomagnetic conditions February 14,
active to disturbed February 15, quiet to unsettled February 16-18,
quiet February 19-20, quiet to unsettled February 21, quiet February
22, quiet to unsettled February 23, mostly quiet February 24, quiet
to active February 25, mostly quiet February 26, quiet February 27
through March 1, mostly quiet March 2, quiet to unsettled March 3,
quiet March 4-6, mostly quiet March 7, quiet to unsettled March
8-10, mostly quiet March 11, and quiet on March 12.

Lew Wallach, N9WL in New Mexico sent a question about the numbers in
parenthesis after the predicted value in smoothed sunspot number
predictions. His example was from

The one I am accustomed to seeing is the prediction in the Weekly
Preliminary Report and Forecast, such as the one on page 21 of a
recent issue at

The numbers in parenthesis represent uncertainty, or the range of
the prediction. Since these are numbers smoothed from data over a
year, the numbers for July 2013 and earlier are known, so there is
no uncertainty. The predicted value for August 2013 of 68 has a one
in the parenthesis, so it could be from 67-69. There is very little
uncertainty, because there is only one month of data that would
figure into the smoothed value that is unknown at the time of
publication, presumably February 2014. As months progress, the
uncertainly becomes larger. You can see that with the prediction
method used in the Weekly report, the maximum range is plus or minus
ten. The forecast method used here is a combination of several
methods, decided on by the Cycle 24 Prediction Panel.

The results are the same as in the table at but resolved to
whole numbers.

This consensus method is described on page 14 of the user guide at .

The reason the numbers are different in the table that N9WL asked
about is the prediction method is one developed in 1949, the
McNish-Lincoln technique. You can see that the bounds, or
uncertainty a few years into the future varies widely from the
method used by the Cycle 24 panel, which go no higher than 10.

The McNish-Lincoln technique is described at

In future years you will notice that the number in parenthesis
exceeds the predicted value. In these cases, the low end of the
range is 0.

John Campbell, K4NFE in Huntsville, AL, sent an article about a
sunspot larger than Jupiter. Read it at .

A similar article is at

Unless you read the Propagation Forecast Bulletin linked from the
ARRL home page, you may have noticed the report in last week's
bulletin about finding a rare first edition of the Radio Amateur's
Handbook. Boy, was I fooled! This was a reproduction published by
the ARRL in 2006 on the ninetieth anniversary of the first edition,
and 20,000 copies were published. These were given to people who
pre-ordered the 2006 edition of the ARRL Handbook. No wonder it was
in such perfect condition. Not only that, but the library system
where I found it has six copies on the shelf. Each has the F.E.
Handy signature, above the words "Personal Copy."

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 web page at For an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at More good
information and tutorials on propagation are at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

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

Sunspot numbers for February 6 through 12 were 223, 241, 186, 180,
122, 151, and 187, with a mean of 184.3. 10.7 cm flux was 191.3,
178, 171.8, 169, 161, 172.2, and 160.1, with a mean of 171.9.
Estimated planetary A indices were 9, 9, 23, 18, 12, 6, and 9, with
a mean of 12.3. Estimated mid-latitude A indices were 5, 7, 19, 11,
9, 3, and 5, with a mean of 8.4.


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