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ARRL Propagation Bulletin ARLP031 (2012)

ARLP031 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 31  ARLP031
From Tad Cook, K7RA
Seattle, WA  August 3, 2012
To all radio amateurs 

ARLP031 Propagation de K7RA

Average daily sunspot numbers this week were up over 47 points to
99.3.  Average daily solar flux rose nearly 35 points to 131.7.
Solar flux jumped from 139.8 on Tuesday, July 31 to 150.1 on
Wednesday, August 1.  Predicted solar flux is 135 on August 3-4, 130
on August 5-6, 125 on August 7-9, 130 on August 10-11, and 120 on
August 12-13.  Solar flux is expected to drop below 100 on August
16-21.  Predicted planetary A index is 8 on August 3, 5 on August
4-19, 8 on August 20-21, 5 on August 22-23, then 8, 8, 12 and 8 on
August 24-27.
At the beginning of August we have some new sunspot data from our
3-month moving average.  The three-month moving averages centered on
January through June 2012 are 83.3, 73.7, 71.2, 87.3, 91.5, and
96.5.  The average centered on June 2012 is every daily sunspot
number from May 1 through July 31 added together, then divided by
the number of days, which is 92.  You could say that this latest
number is the 3-month trailing average, or the 3-month average
centered on June.  Every month we include a new month of data and
drop off an old month.
F.K. Janda, OK1HH says to expect mostly quiet geomagnetic conditions
on August 3-4, active to disturbed on August 5, quiet to unsettled
August 6-7, mostly quiet August 8, quiet on August 9, active to
disturbed again on August 10-11, quiet to active August 12-13,
mostly quiet on August 14-15, and quiet to active on August 16-17.
On the NASA Solar Cycle Prediction page, the only thing that has
changed over the past few months is the date.  This is issued
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 an explanation of
the numbers used in this bulletin, see  An archive of
past propagation bulletins is at  Find more good
information and tutorials on propagation at
Monthly propagation charts between four USA regions and twelve
overseas locations are at
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bulletins are at
Sunspot numbers for July 26 through August 1 were 77, 91, 108, 79,
106, 116, and 118, with a mean of 99.3.  10.7 cm flux was 114.7,
123.3, 126.6, 131.4, 136, 139.8, and 150.1, with a mean of 131.7.
Estimated planetary A indices were 4, 5, 11, 6, 13, 6, and 6, with a
mean of 7.3.  Estimated mid-latitude A indices were 3, 5, 11, 6, 11,
5, and 7 with a mean of 6.9.


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