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ARRL Propagation Bulletin ARLP029 (2016)

ARLP029 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 15, 2016
To all radio amateurs 

ARLP029 Propagation de K7RA

As this solar cycle declines, we will occasionally see periods such
as the past week when activity perks up and it seems that happy days
are back.  Enjoy them when you can, while they last.  Any recovery
is unpredictable and temporary.
Over the past reporting week (July 7 to 13) average daily sunspot
number was 52.6, up 47.7 points from 4.9 in the previous week.  The
previous week's activity was dominated by 5 out of the 7 days with
zero sunspots.
Over the same periods, average daily solar flux rose from 73.1 to
91.6, a healthy advance.
Geomagnetic indices were also active, with planetary A index
advancing 9 points to 15.7 from 6.7 and mid-latitude A index rising
from 8.3 to 14.1 over the same two weeks.
Predicted solar flux is 94 on July 15, 91 on July 16 to 18, 86 on
July 19, 82 on July 20 and 21, then 80, 77, 75, 73, 74, 73 and 72 on
July 22 to 28, then 71, 72, 74, 72 and 77 on July 29 through August
2, then 83, 87, 92, 94 and 92 on August 3 to 7, 90 on August 8 to
13, 85 on August 14, 78 on August 15 and 16, 76 on August 17, and 77
on August 18 and 19.
Predicted planetary A index is 14, 8 and 5 on July 15 to 17, 8 on
July 18 and 19, 5 on July 20 and 21, then 7, 11, 10 and 6 on July 22
to 25, then 4, 6, 7, 9, 8 and 7 on July 26 to 31, and 4 and 5 on
August 1 and 2, 23 on August 3 and 4, then 14, 10, 20, 12, 8, 15 and
10 on August 5 to 11, 5 on August 12 and 13, then 4 and 14 on August
14 and 15 and 12 on August 16 and 17.
Geomagnetic activity forecast for the period July 15 to August 10,
2016 from Petr Kolman, OK1MGW.  Geomagnetic field will be:
Quiet on July 16-17, August 1-2 
Mostly quiet on July 15, 24-26, 31, August 10 
Quiet to unsettled on July 18, 21-23, 30, August 5-7, 9
Quiet to active on July 19-20, 27-29, August 3-4, 8 
Active to disturbed on August (3-4)
Increased solar wind from coronal holes is expected on July 19-21,
27-29, August 2-4, 7-8.
Parenthesis means lower probability of activity enhancement.
Bill Loftus, WA2VQF of Denville, New Jersey (and several others)
sent this article, commenting "Good thing I only need 30 more on 80
meters for 5BDXCC."
Here is a nice resource from Australia's Space Weather Services,
which displays in nice detail solar activity over all of the
historic cycles, starting in 1754.
You might miss this image, which shows all 24 cycles:
Back on April 13, 2016, Ray Bass, W7YKN of Sparks, Nevada (he uses
the phonetics You Know Nothing!) wrote:
"I have a question that so far no one knows the answer to, including
some astronomers and professors.

The numbers for the sunspot groups, like 2230, 2231, 2232 and so
forth are in numerical order but where did they start?
Is there a 0001?  Did they start, at the beginning of a new 11 year
cycle, or when they first started counting sun spots, etc., or did
they start with a higher number than 0001?
So if I started at number 2230 and went backwards to the beginning
where would I be (other than lost)?
We had discussions about this a few times on the air in rag chew
sessions and all were interested but no one knew the answer."

I told Ray that at some time in the past I knew the answer, but have
I forgot about it, then last week Ray wrote to me again, asking if I
had learned anything about this.
It turns out the renumbering begins after sunspot group 9999, and it
starts over at 0.  Note that he was not asking about the sunspot
number, but the numbering of sunspots.  Sunspot number is an
indicator of solar activity, but the numbering of sunspots is just a
method of identifying individual sunspot groups, and it goes from 0
to 9999.  After 10,000 sunspots, the numbers begin all over again.
The last time it did this was June 16, 2002.
Go to, and put June 15, 2002 in the archive
(Spaceweather Time Machine), and you will see sunspots numbered up
to 9998.  The next day they start over at 0 and there is also an
Compare the numbers on the sun on these two consecutive days, 14
years ago:
I solved this by using the Spaceweather archive (Time Machine) and
kept dialing back the years, and noting the numbers on the solar
disc, til I got back to zero.  And right there when they displayed
the transition on June 16, 2002, was this explanation:
"SUNSPOT ZERO:  This weekend NOAA sunspot region numbers reached
9999 and (like a car's odometer) rolled over to 0000.  Sunspot zero
spans an area equal to approximately 0.5 planet Earths.  It is not
particularly large or active -- but it will be easy to remember."

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 July 7 through 13 were 25, 55, 63, 46, 62, 63,
and 54, with a mean of 52.6.  10.7 cm flux was 83.3, 87.1, 92.2,
94.4, 94.7, 92.4, and 96.8, with a mean of 91.6.  Estimated planetary
A indices were 23, 23, 14, 10, 11, 21, and 8, with a mean of 15.7.
Estimated mid-latitude A indices were 19, 18, 15, 11, 11, 18, and 7
with a mean of 14.1.


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