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ARRL Propagation Bulletin ARLP041 (2013)

ARLP041 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 11, 2013
To all radio amateurs 

ARLP041 Propagation de K7RA

Solar activity picked up over the seven days of our reporting week,
October 3-9, and the outlook has improved somewhat. There now are no
predictions for the solar flux dropping below 100 in the next 45
days. October 6 was the date of the last forecast predicting any
flux values below 100. These predictions were for periods later in
October and again in November.

Average daily sunspot numbers increased by 47 points to 79, and
average daily solar flux increased 3.8 points to 110.4. These
averages compare the recent October 3-9 period with the previous
seven days, September 26 through October 2.

The latest prediction for solar flux is 125 on October 11-13, 120 on
October 14-16, 115 on October 17, 105 on October 18-23, 100 on
October 24-29, 105 on October 30-31, 100 on November 1-2, 105 on
November 3-4, 100 on November 5-6, and 105 on November 7-15.

Predicted planetary A index is 10 on October 11-12, 5 on October 13,
8 on October 14-15, 10 on October 16, 8 on October 17, 5 on October
18-20, 10 on October 21, 5 on October 22 to November 6, 10 on
November 7-8, and 8 on November 9-12.

OK1HH predicts geomagnetic activity as quiet to unsettled October
11, mostly quite October 12, quiet October 13, quiet to unsettled
October 14-16, quiet to active October 17-18, quiet October 19-20,
quiet to active October 21, mostly quiet October 22, quiet October
23-27, quiet to active October 28, and active to disturbed October

NBC news has an article about Tuesday's solar flare, which was
strong considering how quiet the Sun has been lately, but was not
aimed directly at Earth. Planetary A index rose to 24 on Wednesday,
October 9, and Alaska's college A index hit 40.

You can read the article at,

Tomas Hood, NW7US, who writes propagation columns for CQ, CQ VHF and
Popular Communications, sent a video he put together concerning a
solar flare mentioned in last week's Propagation Forecast Bulletin

Silverio, IK3IUL sent an inquiry, but replies to him seem to be
bouncing. Perhaps he could try again via another email account.

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 October 3 through 9 were 61, 84, 69, 53, 76, 99,
and 111, with a mean of 79. 10.7 cm flux was 113.8, 109.1, 105.9,
106.5, 112, 111.9, and 113.4, with a mean of 110.4. Estimated
planetary A indices were 6, 2, 1, 2, 6, 16, and 24, with a mean of
8.1. Estimated mid-latitude A indices were 5, 2, 2, 3, 8, 12, and
21, with a mean of 7.6.


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