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ARRL Propagation Bulletin ARLP039 (2018)

ARLP039 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
From Tad Cook, K7RA
Seattle, WA  September 28, 2018
To all radio amateurs 

ARLP039 Propagation de K7RA

The Sun remained spotless over the past week, and by September 27
the period with no sunspots was over two weeks. Average daily solar
flux declined from 68.6 to 67.9. Average planetary A index increased
from 9.7 to 10.9, while average mid-latitude A index declined from
8.3 to 7.9.

Predicted solar flux is 68 on September 28 to October 2, 70 on
October 3-10, 68 on October 11-28, 70 on October 29 through November
6, and 68 on November 7-11.

Predicted planetary A index is 5 on September 28-30, then 8 and 12
on October 1-2, 5 on October 3-6, then 20, 35 and 10 on October 7-9,
18, 15 and 8 on October 10-12, then 5, 10 and 8 on October 13-15, 5
on October 16-17, 10 and 25 on October 18-19, 15 on October 20-21,
then 10 and 8 on October 22-23, 5 on October 24-27, 10 and 12 on
October 28-29, 5 on October 30 through November 2, then 20, 35, 10
and 18 on November 3-6, then 15, 8, 5, 10 and 8 on November 7-11.

Geomagnetic activity forecast for the period September 28 to October
24, 2018 by F.K. Janda, OK1HH.

"Geomagnetic field will be:
Quiet on October 4, 16-17, 20-21
Quiet to unsettled on September 28-30, October 3, 5
Quiet to active on October 1, 6, 11-13, 22-24
Unsettled to active on October 2, 8-10, 14
Active to disturbed on October 7, 15, 18-19

"Solar wind will intensify on October 1-3, 7-8, 12-15, 19-20,

"Remarks: - Parenthesis means lower probability of activity

Thanks to Dick Bingham, W7WKR for forwarding this article by Alex
Schwartz, VE7DXW on his automated space weather station, run with
Raspberry Pi.

If you like his article, Alex would appreciate it if you will
recommend it by clicking on the heart toward the bottom.

Article about a previously overlooked pioneer of radio astronomy:

The latest from Dr. Skov:

"Dear Tad,

"You may be wondering why we've had so many solar storms lately. You
might even have noticed since the last solar storm a week ago that
we haven't yet settled down to quiet conditions. In fact, high
latitude aurora photographers continue to enjoy some pretty decent
light shows despite the solar storm being long over. Just a few
months ago, we seemed to go weeks without any significant activity
here at Earth. So what has changed? The answer is simple: Fall is

"You may think I'm nuts. Few people tend to look at Space Weather as
having seasons like terrestrial weather does. But in truth Space
Weather seasons are very real! As you can imagine, this has very
little to do with the Sun changing its weather patterns during the
year, but it has everything to do with the way the Earth tilts with
respect to the Sun. During the Summer and Winter, the Earth tilts
towards the Sun in such a way as to lessen the impact of Space
Weather. During the Spring and Fall, however, the sideways tilt of
Earth relative to the Sun actually magnifies Space Weather effects.
So just like terrestrial weather, this changing tilt results in
seasons. Generally speaking, Space Weather at Earth maximizes at the
equinoxes and minimizes at the solstices. I will be sure to go into
this phenomenon in more detail in an upcoming live mini-course so I
can share the particulars of how it works. It's called the
'Russell-McPherron effect' and it's really pretty cool.

"This week we are feeling the effects of the Fall Equinox in full
swing. Although we don't really have any strong solar storms en
route, nor are we being battered by any serious fast wind, we just
can't seem to quiet down. We have been sitting at unsettled
conditions for over five days now and we may have a few more days of
this 'Space Weather drizzle' before things relax. Till then, all I
can say is keep your proverbial umbrella handy. Some of this drizzle
can actually help stabilize the upper atmosphere, which improves GPS
reception and amateur radio propagation, so maybe it's worth getting
a little wet.

"Cheers, Tamitha"

Her report is at,

Steve Sacco, NN4X wrote:

"Perhaps this is the enabling factor for SSSP (Short-path Summer
Solstice Propagation) on 6M?  These Electric Blue Clouds Are Made
from Ice Crystals and Meteor Debris"

NASA's PMC Turbo mission captured new views of polar mesospheric
clouds from a five-day balloon flight over the Arctic.

More about SSSP:

Steve also (along with Max, M0VNG) sent info about WWII bombings and
their effects on the ionosphere:

Evan Rolek, K9SQG who has been contemplating 40 meters wrote:

"My observation about 40 meters is that it is virtually dead during
the daytime hours here in Dayton, Ohio. MIDCARS hasn't been heard
here in weeks whenever I have checked. However, in the evening after
9 PM or so, I can hear and work stations all over the country and
there is plenty of space for many, many more QSOs. QSB isn't bad and
signals are strong enabling length QSOs. And if one waits until
after 11 PM local time, working into Germany, Italy, Canary Islands,
etc. is quite easy and all I'm using is a horizontal loop 20 ft off
the ground!

"But, overall, 40M is not what it used to be years ago...'somebody
is always on."'

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
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 20 through 26, 2018 were 0, 0, 0, 0,
0, 0, and 0, with a mean of 0. 10.7 cm flux was 66.6, 66.9, 67.9,
68.4, 68.6, 67.6, and 69, with a mean of 67.9. Estimated planetary A
indices were 2, 9, 27, 12, 7, 11, and 8, with a mean of 10.9.
Estimated mid-latitude A indices were 2, 6, 20, 9, 5, 7, and 6, with
a mean of 7.9.


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