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ARRL Propagation Bulletin ARLP034 (2016)

ARLP034 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 34  ARLP034
From Tad Cook, K7RA
Seattle, WA  August 19, 2016
To all radio amateurs 

ARLP034 Propagation de K7RA

Conditions turned a little more favorable since last week's bulletin
with both solar flux and sunspot numbers up, and geomagnetic indices
substantially lower.
Average daily sunspot numbers for the August 11 to 17 period were
73.9, compared to 52 for the previous seven days.  Average daily
solar flux went from 87.9 to 89.2.  Average daily planetary A index
dropped from 14.6 to 6.9, and average mid-latitude A index went from
13.7 to 7.4.
Predicted solar flux for the near term is 85 on August 19, 80 on
August 20, 75 on August 21 and 22, 85 on August 23 and 24, 90 on
August 25 and 26, 75 on August 27 through September 1, 80 and 85 on
September 2 and 3, and 90 on September 4 to 14.  Solar flux then
pulls back to 75 on September 18 to 28, then recovers to 90 in the
first days of October.
Predicted planetary A index is 10, 14, 8 and 6 on August 19 to 22, 5
on August 23 and 24, 12 on August 25, 8 on August 26, 5 on August 27
and 28, then 15, 25 and 18 on August 29 to 31, 15 on September 1 and
2, 12 on September 3 and 4, and 15 on September 5 and 6.
The predicted planetary A index is 25 on September 26, indicating
high geomagnetic activity.
We have a geomagnetic forecast from F. K. Janda, OK1HH. 
The geomagnetic field will be, 
Quiet on August 22, 27 and 28, September 10 to 12 
Mostly quiet on August 19, 23, 26, September 9 
Quiet to unsettled on August 20, September 1, 13 
Quiet to active on August 21, 24 and 25, 31, September 2 to 8, 14 
Active to disturbed on August 29 and 30 
Increases of solar wind from coronal holes are expected on August
(24 and 25, 29,) 30 and 31, September 1, (2 to 5)
- Parenthesis means lower probability of activity enhancement. 
Thanks to David Moore for sending this article about the Van Allen
Note that it mentions a big geomagnetic storm last year on March 17,
so I thought it would be interesting to see what the numbers looked
Those are some big numbers indicating a big disturbance.  Note also
that the middle column, which is data for Alaska's College A index
shows that the instruments were offline or there was some kind of
problem gathering data in the four days preceding the big numbers.
Unsure if this had anything to do with the impending storm, or if
they just got lucky and had everything back online by the day of the
big event.
Don't miss the link half way down the right side of the page on the
Van Allen article, titled "Chemtrails Not Real, Say Atmospheric
Science Experts."  Nothing to do with radio or propagation, but it
has some interesting facts about a popular belief that I regard as
popular folklore.
I noticed in yesterday's ARRL DX bulletin that there are a lot of
scheduled island (IOTA) and lighthouse operations coming up this
weekend and beyond.
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  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 August 11 through 17 were 82, 86, 73, 61, 70,
81, and 64, with a mean of 73.9. 10.7 cm flux was 94.7, 94.8, 90.5,
87.2, 87.6, 86.5, and 82.9, with a mean of 89.2.  Estimated
planetary A indices were 9, 11, 5, 4, 4, 6, and 9, with a mean of
6.9. Estimated mid-latitude A indices were 8, 11, 5, 4, 4, 8, and 12
with a mean of 7.4.


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