ARRL Propagation Bulletin ARLP038 (2013)

ARLP038 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 38  ARLP038
From Tad Cook, K7RA
Seattle, WA  September 20, 2013
To all radio amateurs 

ARLP038 Propagation de K7RA

Solar activity continues to be weak, although there was an uptick on
September 18-19 when solar flux rose to 104.1, then 107.9. September
18 was the first day with solar flux above 100 since September 6.
Average daily sunspot number for the reporting week (September
12-18) rose to 42.3, up from 37.7 for the previous seven days. The
daily sunspot number on September 18-19 rose from 59 to 85.

Average daily solar flux dipped slightly, from 98.2 to 95.3 over the
same seven day period. Average daily planetary A index and
mid-latitude A index were both 6.3.

For the near term, solar flux is predicted at 110 on September
20-22, 105 on September 23-24, 100 on September 25-30, 95 on October
1-13, and 100 on October 14-27. Over the past few days all of the
short term predictions for solar flux have been adjusted downward.

Predicted planetary A index is 8 on September 20, 5 on September
21-22, 8 on September 23-24, 5 on September 25-26, 8 on September
27, 12 on September 28, 5 on September 29 through October 9, then
10, 8, 5, 15, 10 and 8 on October 10-15, followed by 5 on October

OK1HH sent us another geomagnetic forecast, and he thinks the
geomagnetic field will be quiet to unsettled on September 20-21,
mostly quiet September 22, quiet to unsettled on September 23, quiet
on September 24-25, mostly quiet September 26, active to disturbed
September 27, quiet to active September 28, mostly quiet September
29, quiet on September 30, quiet to active October 1, quiet on
October 2-5, quiet to unsettled October 6-7, mostly quiet October 8,
and active to disturbed October 9.

OK1HH also says a growing solar wind may cause "remarkable changes"
in the magnetosphere and ionosphere on September 20-21, and on
September 24.

The Autumnal Equinox is just a couple of days away. Fall officially
begins in the Northern Hemisphere on Sunday, September 22 at 2044

Check out this science blog, with observation about the current weak
cycle at,

The following interesting article has a lot of good information,
surprising (to me) for an article from a financial and markets
analyst who is not a science reporter.

The only minor quibble I have is with his apparent confusion between
number of sunspots and sunspot number, which are very different, but
otherwise this article is quite a good effort:

Howard Lester, N7SO sent this article from Sky & Telescope.

Jon Jones, N0JK commented on N8II's recent report, and says that 10
meters has been good in Kansas as well, with F0/KH0PR on
Disappointment Island worked on September 11 at 1955 UTC from his
mobile using a modified CB mag mount on the roof.

Roland Anders, K3RA also commented on N8II's experience, "Jeff's
excellent report about 12 meters prompts me to pass along that there
was some 12 meter excitement in Maryland on Sept 10 around noon. I
worked 9M6XRO at 1538Z on CW, and E20WKA on SSB at 1603Z. VOACAP
modeling shows that possibility. European stations were coming
through at the same time."

Larry Godek, W0OGH sent these links for checking sunrise/sunset
times around the world: and .

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

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bulletins are at

Sunspot numbers for September 12 through 18 were 58, 40, 24, 12, 23,
80, and 59, with a mean of 42.3. 10.7 cm flux was 92.9, 91.6, 92.5,
92.8, 94.5, 98.7, and 104.1, with a mean of 95.3. Estimated
planetary A indices were 7, 9, 6, 2, 5, 8, and 7, with a mean of
6.3. Estimated mid-latitude A indices were 5, 10, 6, 3, 6, 8, and 6,
with a mean of 6.3.