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ARRL Propagation Bulletin ARLP012 (2018)

ARLP012 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 12  ARLP012
From Tad Cook, K7RA
Seattle, WA  March 23, 2018
To all radio amateurs 

ARLP012 Propagation de K7RA

At 2332 UTC on March 22 the Australian Space Forecast Centre issued
a geomagnetic disturbance warning for this weekend, March 24 and 25.
"Expect the geomagnetic activity to increase to mostly Active levels
with isolated periods of Minor to Major Storm levels due to a high
speed solar wind stream associated with a negative polarity coronal
hole becoming geo-effective".

In last week's report, ARLP011, there were no sunspots over the
reporting week.  On March 15 one new sunspot appeared for a sunspot
number of 11, which is the minimum non-zero sunspot number.  The
next day it was gone, then a new sunspot appeared March 17.  Sunspot
numbers on March 17 and 18 were 15 and 13, then none for the rest of
our reporting week, March 19 to 21.  So the average daily sunspot
number increased from 0 over the previous week to 5.6 over the most
recent 7 days, ending Wednesday March 21.

Average daily solar flux over the same two periods increased from
67.7 to 69.3.  Geomagnetic indices about doubled, with average
planetary A index changing from 7.1 to 14.4, and mid-latitude A
index increasing from 5.7 to 11.3.

Predicted solar flux is 68 on March 23 through April 2, 69 on April
3 and 4, 70 on April 5 to 15, 69 on April 16 and 17, 68 on April 18
to 29, 69 on April 30 through May 1, and 70 on May 2 to 6.

Predicted planetary A index is 8, 22, 24, 18 and 8 on March 23 to
27, 5, 15, 10 and 8 on March 28 to 31, then 5 on April 1 to 9, then
8, 15 and 20 on April 10 to 12, then 15 on April 13 and 14, then 8
and 12 on April 15 and 16, 18 on April 17 to 19, 15 and 8 on April
20 and 21, and 5 on April 22 to 25, 8 on April 26 and 27, and 5 on
April 28 through May 6.

The spring equinox began at 1615 UTC on Tuesday, March 20 in the
Northern Hemisphere.  At that moment solar radiation was equally
distributed between the Northern and Southern Hemisphere.  Except
for the low solar activity, the beginning of spring should be an
ideal time for worldwide HF communication.

Geomagnetic activity forecast for the period March 23 to April 17,
2018 from F. K. Janda, OK1HH.

"Geomagnetic field will be:

Quiet on April 3, 7 to 9
Mostly quiet on March 28, 30, April 6
Quiet to unsettled on March 26 and 27, 31, April 1 and 2, 4 and 5,
16 to 18
Quiet to active on March 23 to 25, 29, April 10 and 11, 13, 15
Active to disturbed on March 26, April 12, 14

Solar wind will intensify on March 25 to 28, (31,) April (6 to 8,)
10 to 18

- Parenthesis means lower probability of activity

Scott Bidstrup, TI3/W7RI sent this article:

Scott's observation was that the rogue sunspots toward the end of a
solar cycle suggest a weaker subsequent cycle.  But I was pleased to
see the article suggest that the rogue sunspots could suggest a
strong cycle like cycle 19 at the end of the 1950s.  That would be

Scott also wrote:

"Well, down here in the single-digit latitudes, the declining solar
cycle has had some interesting effects on propagation.  Ten meters
has been opening almost every day, sometimes as early as 9AM local
time, and providing quite reliable communications into South America
through most of the day.  By local noon, the FT8 window on ten
meters often looks like the window on twenty, packed with signals
end to end, but most days into the same region - southern Brazil,
Argentina and Uruguay, occasionally with Chile.  It has all the
characteristics of afternoon TEP openings.  Almost every day, the
band will be open until 3PM or 4PM local time, when it will suddenly
fold, in just ten minutes going from wide open to flat dead.

My daily sunrise coffee klatch with the local gringo hams on 75m has
been affected by the very low solar activity, too.  We usually kick
off around local sunrise, but the band has been failing to shorten
up for local propagation, often failing to open till as much as an
hour after local sunrise.  Lately, the band opening has not only
been late, it's been remarkably sudden when it does happen, often
going from almost no local signal at all, to the strong S9+10
signals in as little as a minute.  It's like God's flipping a
switch.  One of the more odd aspects of this is that when this
transition occurs, the DX signals occasionally don't fade out for
half an hour or more, and we've had to move our frequency because of
frequent Stateside QRM on the frequency we've been using without a
problem for years.  More than once, we've had roundtables with
Stateside stations that were as strong our local stations were - at
least until the D-layer finally kicks in and they're faded out and
gone.  Occasionally, the DX fades well before the local propagation
opens up, too.  It's all very unpredictable.

160 meters down here has greatly benefited from the FT8 revolution
as well as the improved conditions for top band at the bottom of the
solar cycle.  Seems that lots of the locals, me included, have
discovered that a hundred watts into a force-tuned 80m antenna will
produce useful results on 160m FT8.  In my own case, I've worked a
number of European stations, including Belarus and Greece, using
nothing more than 60 watts into a G5RV antenna at 50 feet.  The best
DX seems to be appearing about two hours after the band opens at
sunset.  My good friend Jay, HP3AK, has worked a couple of dozen
European and Far East stations using a 60 foot folded 160m vertical
monopole with only seven radials.  All in all, it's been a lot of
fun being able to actually work someone on top band here without
going to all the effort of putting up a dedicated antenna. With all
our atmospheric noise here, this is a new experience for most all of

The CQ World-Wide WPX SSB Contest is this weekend.  See

For more information concerning radio propagation, see the ARRL
Technical Information Service at  For an explanation of
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 March 15 through 21, 2018 were 11, 0, 15, 13, 0,
0, and 0, with a mean of 5.6.  10.7 cm flux was 69, 68.6, 69.7,
69.1, 70.3, 68.8, and 69.3, with a mean of 69.3.  Estimated
planetary A indices were 15, 20, 13, 25, 16, 8, and 4, with a mean
of 14.4.  Estimated mid-latitude A indices were 13, 17, 10, 16, 13,
7, and 3, with a mean of 11.3.


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