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ARRL Propagation Bulletin ARLP031 (2015)

ARLP031 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 31  ARLP031
From Tad Cook, K7RA
Seattle, WA  July 31, 2015
To all radio amateurs 

ARLP031 Propagation de K7RA

At 0132 UTC on July 30 the Australian Space Forecast Center issued a
geomagnetic disturbance warning, saying a high speed solar wind from
a recurring coronal hole is expected to raise geomagnetic activity
levels to minor storms on July 31 and August 1. They predict quiet
to minor storm levels on July 31 and minor storm declining to
unsettled conditions on August 1.
Solar activity currently remains in the doldrums, with average daily
sunspot numbers rising just 4.5 points to 47.9 during the July 23 to
period from the prior week.
Average daily solar flux over the same periods rose just 1.5 points
to 96.4.
When I look at the solar disc displayed at
I count six numbered sunspot groups, but they are not magnetically
complex, and the types of radiation we need to energize our
ionosphere is weak.
The most active geomagnetic day was July 23, when the planetary A
index was 23 and the mid-latitude A index was 21. That day there was
a mild geomagnetic storm caused by a coronal mass ejection that did
not hit earth directly.
Predicted solar flux is 105 on July 31 through August 2, 110 on
August 3 to 5, 115 on August 6, 110 on August 7, 100 on August 8 and
9, 95 on August 10 to 13, then 90 and 85 on August 14 and 15, and
100 on August 16 and 17. Solar flux peaks at 115 on August 28 to 31,
then drops below 100 after September 5.
Predicted planetary A index is 18 on July 31, 24 on August 1, then
16, 12 and 8 on August 2 to 4, then 5, 8 and 20 on August 5 to 7,
then 15 on August 8 and 9, and 8 on August 10, 5 on August 11 to 15,
10 on August 16, 5 on August 17 and 18, then 15 and 10 on August 19
and 20, and 5 on August 21 to 23.
OK1MGW predicts the geomagnetic field will be active to disturbed on
July 31 and August 1, quiet to active August 2, mostly quiet August
3 to 5, quiet to active August 6, active to disturbed August 7 and
8, quiet to active August 9, quiet to unsettled August 10 and 11,
quiet August 12 to 14, mostly quiet August 15, quiet to unsettled
August 16, mostly quiet August 17, quiet to active August 18, quiet
to unsettled August 19 to 22, and mostly quiet August 23 to 26.
He expects increased solar wind on July 31 through August 3, and
again on August 6 to 9.
Rich Camp, WA7VGN of Las Vegas, Nevada wanted to be sure meteor
showers also occur during daylight. Yes, they do, and you can make
contacts via meteor scatter day and night.
Jon Jones, N0JK passed along a good resource for meteor scatter,
Ping Jockey Central:
Jon mentioned this will be a great tool for checking activity during
the upcoming Perseids Meteor shower, which is August 11 to 14 this
Jon also passed along some sporadic-E news:
"The summer 2015 North America Sporadic E skip season is winding
down. Usually the peak period is around the summer solstice through
the first week to 10 days of July.
Some late season July Es continued. On July 21, PR8ZX GI64 in Brazil
worked into the Midwest on 6 meters and was spotted 599 by K2DRH at
2239z. This was multi-hop Es to the geomagnetic equator.
A strong 6 meter opening between Arizona, California and Washington
State to Japan took place July 24 and 25.
On the July 26, CO8LY FL20 worked into the Midwest and Rocky
Mountain states via double hop Es. Spotted by K0GU DN70 and NW0W
EM47 until 1650z. I logged him on 50.108 MHz at 1758z."
Jon also passed along this late news: "July 30, J69MV, VP2ETE, FG8OJ
and KV4FZ were in to IA, MO, OK and W4 around 1630z via double hop
E-skip on 50 MHz."
Check this map for live lightning detection across North America:
This was passed on by Dick Bingham, W7WKR who lives way off the grid
at Stehekin, Washington, which is at the northwest end of Lake
He advises making sure Strikes, Detectors Used and Sound are turned
on for the lightning app.
Also check these pages:
Pierre Desjardins, VE2PID of Sherbrooke, Quebec asked about the
predicted International Sunspot Number at
and what the numbers in parenthesis mean.
The numbers above the parenthesis are predicted smoothed
international sunspot numbers, which use a 13-month average.  A zero
means there is zero uncertainty about the number, because all of the
data used to calculate this smoothed number are known values. But as
we move into the future, there is more uncertainty. For the latest
month, we already know half the data used to calculate the average,
but the other half of the data is predicted.  So the higher numbers
in parenthesis indicate greater uncertainty.
Rob Steenburgh, AD0IU who works as a space weather forecaster at
NOAA said the predictions here are from the McNish-Lincoln
technique, from a paper published in 1949.  The method is described
Rob is checking with a colleague to find out exactly what the
numbers represent and perhaps the scale used.
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
My own archives of the NOAA/USAF daily 45 day forecast for solar
flux and planetary A index are in downloadable spreadsheet format at and .
Click on "Download this file" to download the archive and ignore the
security warning about file format. Pop-up blockers may suppress
download. I've had better luck with Firefox than IE.
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 23 through 29 were 27, 54, 41, 38, 53, 56,
and 66, with a mean of 47.9.  10.7 cm flux was 89.4, 92.2, 94, 97,
100.1, 101.1, and 100.7, with a mean of 96.4. Estimated planetary A
indices were 23, 7, 9, 8, 11, 9, and 5, with a mean of 10.3.
Estimated mid-latitude A indices were 21, 6, 9, 9, 13, 9, and 7,
with a mean of 10.6.


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