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ARRL Propagation Bulletin ARLP037 (2016)

ARLP037 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 37  ARLP037
From Tad Cook, K7RA
Seattle, WA  September 9, 2016
To all radio amateurs 

ARLP037 Propagation de K7RA

Compared to the last reporting week, this week (September 1-7)
average daily sunspot numbers were down, solar flux increased, and
geomagnetic indices were much more active.

Average daily sunspot number declined from 60.1 to 46.4, while
average solar flux went from 87.9 to 95.1. Average planetary A index
increased from 8 to 26.6, while average mid-latitude A index rose
from 6.9 to 18.1.

The daily planetary A index on September 1-4 was 36, 39, 40 and 28.
It looks like an echo of the solar wind which caused this activity
is expected on September 28 through October 1, when the predicted
planetary A index is 35, 38, 40 and 25.

Predicted solar flux is 95 on September 9-10, then 92, 90, and 85 on
September 11-13, 80 on September 14-16, 108 on September 17-19, then
110, 105 and 110 on September 20-22, 112 on September 23-24, 108 on
September 25, 105 on September 26-27, 100 on September 28, 95 on
September 29 through October 1, 98 on October 2-4, 95 on October
5-6, 90 on October 7-8, 95 on October 9, 100 on October 10-11, 105
on October 12, and 108 on October 13-16. After October 16 flux
values meander from 105 to 112.

On September 5 predicted solar flux values for September 13 to
October 21 got a big boost, a predicted increase ranging from 18-30
points from the September 4 prediction.

Predicted planetary A index is 15 on September 9, 8 on September
10-11, 10 on September 12, 8 on September 13-15, 5 on September
15-16, then 8, 5, 15, 12 and 8 on September 17-21, 5 on September
22-25, then 12, 8, 35, 38 and 40 on September 26-30, then 25, 20 and
12 on October 1-3, 10 on October 4-5, 5 on October 6-9, then 10, 8,
5, 5, 8, 5, 15, 12 and 8 on October 10-18, and 5 on October 19 and

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

Quiet on September 23-24
Mostly quiet on September 9-11, 14-16, 18, 22, October 5
Quiet to unsettled on September 12, 17, 21, 25, 27, October 3-4
Quiet to active on September 13, 19-20, 26, 28-30, October 1-2
Active to disturbed on September (29-30)

Increased solar wind from coronal holes is expected on September
12-13, 17, 19-21, 25-26, 28-30, October 1-2

Remarks: - Parenthesis means lower probability of activity

Propagation expert Carl Luetzelschwab, K9LA gave a talk (via the
Internet) to the World Wide Radio Operator's Foundation on August
23, as reported this week on the ARRL web site:

Also note the link in the article to Carl's presentation to the
club, "Solar Topics - Where We're Headed." See/hear it at .

Carl notes that some forecasters of space weather have predicted
smaller solar cycles in the future. But personally, I would not be
so sure (I'm always searching for something to be positive about,
when it relates to future solar activity).

Check out this presentation by Douglas Biesecker, Chair of the Solar
Cycle 24 Prediction Panel,, which does not
predict low solar activity extending decades into the future.

Note also that Carl predicts a future Cycle 25 at least as strong as
Cycle 24.

Carl also mentioned a number I had not heard before. He notes that
many solar cycles in the past have been equivalent to Cycle 19, the
biggest sunspot cycle experienced by anyone still alive today. He
projects back over the past 11,000 years, and with the number he
gives, the next grand maximum after Cycle 19 in the late 1950s might
be around year 2537 AD. Note that Carl did not predict this. I am
just trying to extrapolate from the numbers he mentioned, to get
some very rough idea of how uncommon Cycle 19 was.

His numbers show that over the past 11,000 years, 19 notable grand
maximums - including Cycle 19 and the cycles around it - and 27
notable grand minimums were recorded. "We're likely to have more of
both grand maximums and grand minimums in the future," he predicted.
But arithmetically estimated from 19 maximums in 11,000 years, that
puts the next big one (after Cycle 19) at 521 years from now, maybe
in Cycle 71.

Finally, we received a note from Dick Ferry, K2KA of Westford,
Massachusetts concerning 6-meter auroral propagation on September 3:

"Some notes of last night's brief AU opening.

"Got up at 1230am (0430Z) Sep 3, saw AU activity on 6M.

"I heard KL7NO on 50.1056 MHz.  He was very weak, barely copiable
but I did hear him. Didn't call him as he was only audible for a few

"That would have been awesome!

"Did call CQ for about 5 min.

"K0KP/B, N8PUM/B and VE4VHF/B were loud. But no humans on the band.
The beacons were gone in about 10 min.

"73, Dick K2KA (formerly AB1A)."

Thanks Dick!

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 September 1 through 7 were 66, 50, 46, 59, 22,
32, and 50, with a mean of 46.4. 10.7 cm flux was 95.2, 94.6, 99,
97.4, 93.8, 92.4, and 93, with a mean of 95.1. Estimated planetary A
indices were 36, 39, 40, 28, 17, 14, and 12, with a mean of 26.6.
Estimated mid-latitude A indices were 29, 24, 21, 20, 13, 12, and 8,
with a mean of 18.1.


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