Secure Site Login

ARRL Propagation Bulletin ARLP027 (2016)

ARLP027 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 27  ARLP027
From Tad Cook, K7RA
Seattle, WA  July 1, 2016
To all radio amateurs 

ARLP027 Propagation de K7RA

Eight days with no sunspots, at least so far. Average daily sunspot
number for our reporting week was down 33.6 points to 0. Earlier in
this month we saw four days with a blank Sun (sunspot number of 0)
from June 3-6.

There were no sunspots during all of Field Day weekend.

The last time we saw a blank Sun (before June 2016) was 2014. Just
one day, on July 17, 2014. Sunspot number was 0, and only for one
day. Prior to that, there were just two days in 2011, on January 27,
and on August 14.

Prior to that there were 51 days with a blank Sun in 2010, with 12
periods ranging from 1 to 13 days. The longest periods were 11 days
beginning on May 9, 2010 and 13 days beginning on April 1, 2010.

These recent periods of no sunspot activity are a surprise to me,
even though we are in a declining half of the solar cycle. I didn't
expect the extended periods with no sunspot activity would begin so
early following the peak of Solar Cycle 24. But perhaps we will see
some extended periods of more sunspot activity, since we've seen in
the past that nothing moves in a straight line up or down. There is
plenty of variation.

Or perhaps that reference to memory suggests the classic gambler's
fallacy. This refers to the illogical feeling that because a
particular ball in the lottery hasn't been drawn for a long time
that somehow it is overdue, making it more likely that the numbered
ball will be drawn soon. This, of course, concerns only a random
draw with all independent variables.

Mentioned earlier was the observation that the average daily sunspot
number was 0 over our reporting week (June 23-29) compared to 33.6
on the previous seven days. Average daily solar flux during the same
two weeks dropped from 83.8 to 75.6.

Average daily planetary A index increased from 7 to 9, while the
mid-latitude A index went from 6.9 to 9.1.

The latest prediction (June 30) sees solar flux at 75 on July 1-7,
80 on July 8, 80 on July 11, 82 on July 12-13, 80 on July 14-17, 78
on July 18-23, 77 on July 24 and 80 on July 25-31. Following this,
the prediction shows solar flux rising two points for the first week
in August.

Predicted planetary A index is 12, 30, 25, and 10 on July 1-4, 5 on
July 5-7, then 10 on July 8-9, then 8, 20, 12 and 5 on July 10-13, 8
on July 14-15, 5 on July 16-18, then 15, 12 and 10 on July 19-21,
and 5 on July 22-26, 10 on July 27 and 8 on July 28-29.

OK1MGW sends us his geomagnetic activity forecast for the period
July 1-July 27, 2016.

Geomagnetic field will be: 

Quiet on July 16-17, 26-27 
Mostly quiet on July 1, 6, 14-15, 18, 24-25 
Quiet to unsettled on July 4-5, 10, 13, 21-23 
Quiet to active on July 7-9, 11-12, 19-20 
Active to disturbed on July 2-3

Increases in solar wind from coronal holes are expected on July 2-3,
7-9, 11-12, and 19-20.

In line with the USAF/NOAA planetary A index forecast and the OK1MGW
prediction, the Australian Space Weather Services issued a
geomagnetic disturbance warning at 2346 UTC on June 30.

Geomagnetic conditions on July 2-3 are expected to increase to
Active levels and at times possibly reaching Minor Storm levels in
response to the high speed solar wind emanating from an equatorial
coronal hole.

Expect quiet to minor storm levels on July 2 and quiet to active
July 3.

Conditions were good during ARRL Field Day last weekend.  There were
no sunspots but there were also no massive solar eruptions or
geomagnetic storms.

Taking a quick look at our 3-month moving average of daily sunspot
numbers ending June 30, the numbers starting with the three months
ending on January 31 were 55.4, 53.5, 49, 45.3, 43.1 and 35.4.  The
falling progression continues. Our latest period at 35.4 is the
lowest in the current cycle since the three months centered on
January 2011, when the 3 month average was 35.3.

The last minimum was around August 2008 to March 2009.

Here is a recent article about the lack of sunspots:

Lou, VK5EEE sent in a couple of interesting questions, which I
passed on to Carl, K9LA.

Here was Lou's first question.

"I have observed on several occasions over the past 6 months or so,
an unusual propagation, which I cannot explain. I have searched far
and wide on the Internet, and short of an atmospheric nuclear
explosion causing a strong ionization of E layer, which does not
appear to have occurred based on Geiger counter readings, I find no

"Sporadic-E, we are told, occurs from around 12m (25MHz) upwards, is
that correct? Can it occur on 21MHz? CAN IT EVER OCCUR on 20m? It
appears to me not on 20m. Also, what I describe does not last a
short time, as would be expected, but for hours. Short skip of 600km
AT NIGHT on 20m, this should not normally be possible?

"At the same time as this short skip late evening propagation from
VK5 to VK3 (dipole facing broadside to VK3 and HS at my VK5 QTH) the
VK3 was using 5 element beam up 20m beaming to HS (same direction as
VK5) and HS was beaming to VK3 with a 4ele beam up 22m. The VK3-VK5
was exceptionally strong 599+20dB on my 8m high dipole. Not to be
expected, even more so with a 5ele beam during the middle of the
day, most of the energy should pass way overhead. The VK3-HS were
both 599 to each other, but HS-VK5 was only S4 from me, S7 from HS.

"Given it is taking place, and the phenomenal signal strengths, 20
or so dB above what would be normal via F layer propagation, would
that be E layer propagation, and why is the E layer there?"

Carl, K9LA responded:

"With respect to your observation number 1, I downloaded ionosonde
data from Canberra (the closest to your VK5 to VK3 path - we can get
a general idea of what happened in the ionosphere) for Jan 1, 2016
to May 31, 2016. That's 152 days of data, and data is taken every
hour - that gives 3648 possible data points.  For an E mode (110 km
height), the elevation angle for the 600 km path is around 18
degrees. The value of foE must be greater than about 5 MHz to
support 14 MHz for this short path. For an F mode (300 km height),
the elevation angle is around 45 degrees. The value of foF2 must be
greater than about 9.3 MHz to support 14 MHz.  The foE data had 847
data points, so there is a lot of data missing. Of the data
available, there's nothing above 4.5 MHz.  The foEs data had 1759
data points. That's better - almost 50% of the possible data points.

"In your summer (January and February), there are many foEs values
above 5.0 MHz. Towards your winter (May), there are still quite a
few foEs values above 5.0 MHz.  The foF2 data had 2887 data points
(about 80% of the possible total). There were not many foF2 values
above 9.3 MHz. Most foF2 values were 7 MHz and below.  This cursory
investigation suggests that Es could have been the mode. But your
question asking if Es occurs on 20-Meters is very relevant.  With Es
layers being thin (I've seen values from 1 to 5 km), there just
isn't enough vertical extent of the layer to have pure refraction
(bending) take place, and the ionization doesn't appear to be enough
for reflection.

"Thus in my mind the answer to your question appears to be 'no, Es
generally doesn't happen on 20-Meters.' If foEs was much higher,
then a thin layer might support reflection at 14 MHz.  There is an
'above-the-MUF' mode with both the E region and F region when the
operating frequency is somewhat above the MUF. This mode is believed
to involve a scatter mechanism, which implies additional loss. Using
the 'above-the-MUF' estimates of additional loss on 14 MHz says your
observations could have been either E or F.  And there's also the
possibility of a back-scatter mode, with the scatter region being
somewhere northwest of you along the path to HS.

"That's about as far as I can go with this. I don't have a definite
answer - that happens more than we'd like with some HF propagation
observations due to the lack of suitable ionospheric data."

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 June 23 through 29 were 0, 0, 0, 0, 0, 0, and 0,
with a mean of 0. 10.7 cm flux was 77.5, 75.7, 77.1, 76.6, 75.4,
73.1, and 73.6, with a mean of 75.6. Estimated planetary A indices
were 12, 12, 7, 11, 10, 7, and 4, with a mean of 9. Estimated
mid-latitude A indices were 10, 10, 7, 11, 16, 6, and 4 with a mean
of 9.1.