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ARRL Propagation Bulletin ARLP020 (2016)

ARLP020 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 20  ARLP020
From Tad Cook, K7RA
Seattle, WA  May 13, 2016
To all radio amateurs 

ARLP020 Propagation de K7RA

There was a whopper of a geomagnetic storm on Mother's Day, May 8,
when the planetary A index reached 70. In Alaska, the college A
index was 117. Aurora was visible in North America well south of the
northern tier states.

Average daily sunspot number dropped 15.6 points to 59.1 over the
past week, and average daily solar flux declined 3.1 points to 88.8.

Average daily planetary A index over the same period doubled from
11.3 to 22.6, and average daily mid-latitude A index rose 3.9 points
to 14.6.

The latest prediction has planetary A index at 5 on May 13-14, then
8, 15, 12, 6, 5, 15 and 12 on May 15-21, 5 on May 22-23, 10 on May
24, 5 on May  25-27, then 10, 25 and 10 on May 28-30, 5 on May 31
through June 1, 12 on June 2-3, then 30, 32, 25, 15 and 8 on June
4-8, and 5 on June 9-10. Planetary A index then rises to 25 on June
25, but that is a long way off.

Predicted solar flux is 95 and 97 on May 13-14, 100 on May 15-16,
then 95, 93, 90 and 85 on May 17-20, 82 on May 21-22, 85 on May
23-25, 90 on May 26-30, 88 on May 31 through June 2, 85 on June 3-6,
90 on June 7-9, 95 on June 10-11, then 90 and 85 on June 12-13, 82
on June 14-18, and 85 on June 19.

Petr Kolman, OK1MGW of the Czech Propagation Interest Group says the
geomagnetic field will be:

Quiet on May 16-17, 25-26
Mostly quiet on May 15, 22-24, 31, June 7-8
Quiet to unsettled on May 13-14, 18, 21, 27, 30
Quiet to active on May 19-20, 28-29, June 1-2, 3, 6
Active to disturbed on May (28), June 4-5

Increases in solar wind from coronal holes are expected on May
19-21, 28-29, June 1-6

Parenthesis means lower probability of activity enhancement.

We missed it last week, but here is the latest update on our 3-month
moving average. According to our numbers, Solar Cycle 24 peaked with
a sunspot number of 148.2 in the three months centered on March

Beginning with the 3 months centered on January, 2015, the 3-month
moving average of daily sunspot numbers was 98.2, 78.1, 68.2, 72.4,
77.7, 76.3, 69.1, 67.5, 64.5, 64.6, 58.5, 55.4, 53.5, 49 and 45.3.
The numbers reflect the steady decline of Solar Cycle 24.

According to it looks like the next solar
minima should be in 2019. These are international sunspot numbers,
but the sunspot numbers we report in this bulletin are from the NOAA
Space Environment Service Center, .

David Moore sent this piece from Science Daily about solar wind:

Now here is a surprising and counter-intuitive assertion. claims "When sunspots are minimal, the solar
magnetic field is at a maximum."

As mentioned in last week's bulletin, Carl, K9LA offers the W6ELProp
installation file if you have trouble downloading it from

Note that the latest version of W6ELProp is Version 2.70, which was
in the 2002 time frame. Thus it is likely that Shel, W6EL never
checked it out with newer operating systems like Vista and Windows
7, 8 and 10. Shel, W6EL became a Silent Key in April 2015, and as
far as Carl is aware the source code for W6ELProp was never released
to anyone.

If anyone has successfully installed W6ELProp on a PC using Vista or
Windows 7, 8 or 10, Carl would like to hear from you. Carl can be
reached via email at,

Actually I have run it successfully on Windows 7 and 10, but Carl
pointed out that the Maps feature doesn't work.

The Solar Plotting Utility mentioned in past bulletin doesn't run on
Windows 7 or 10, but that is easily solved by running Windows Xp as
a virtual machine within the newer Windows versions.

In Windows 10 it is also possible to run older programs in
Compatibility Mode.

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 May 5 through May 11 were 55, 56, 51, 42, 68,
70, and 72, with a mean of 59.1. 10.7 cm flux was 87.1, 89.6, 88,
85.6, 88.5, 88.7, and 93.9, with a mean of 88.8. Estimated planetary
A indices were 8, 15, 10, 70, 33, 16, and 6, with a mean of 22.6.
Estimated mid-latitude A indices were 7, 12, 9, 32, 21, 15, and 6,
with a mean of 14.6.


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