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ARRL Propagation Bulletin ARLP012 (2008)

ARLP012 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 12  ARLP012
From Tad Cook, K7RA
Seattle, WA  March 17, 2008
To all radio amateurs 

ARLP012 Propagation de K7RA

This is an off-schedule propagation bulletin based on last Friday's
release, Propagation Forecast Bulletin ARLP011.  There will be
another off-schedule bulletin on Thursday, March 20, because ARRL
headquarters will close for the Good Friday holiday.

The reason for this Monday morning bulletin is to correct some bad
data we obtained from issue 1697 of the weekly Preliminary Report
and Forecast of Solar Geophysical Data from the NOAA Space Weather
Prediction Center.

Readers who clicked on the link to issue 1697 in last week's
bulletin may have wondered what we were referring to when we
heralded a new prediction for a more robust Cycle 24, and talked
about changes from the first week of January forecast in issue 1687.

After I emailed a forecaster in Boulder about the new prediction, he
responded "What new prediction?", and Friday morning corrected the
data.  Apparently nobody had noticed the new numbers, in a table on
page 9 of issue 1697, when it was released on Tuesday.

I sent my email Thursday night, and I understand they are reviewing
the process used to publish these numbers.  They were so sorry about
the mistake that they even offered to let me be announcer for a day
on the 18-minutes-after-each-hour bulletin of solar flux and
geomagnetic data transmitted by WWV, if I ever visit Colorado.
Can't be sure if they were serious, but I promised not to use my own
call sign.

I understand that currently the numbers for the table are
hand-typed, with the data coming from, and  The URL
ending in high.txt shows the prediction from the forecast team that
believes the next cycle will be robust, and the URL ending in
low.txt is from the group which thinks Cycle 24 will be weak.  They
have averaged the two predictions, and show them in  Note that all
three tables show a high and low range, and these reflect what each
team thinks the likely range of values could be.

Note that both teams predict the cycle bottom was in February 2008.
Last month's value is still a prediction, because these are smoothed
sunspot numbers, averaged over a year.  So February's numbers are an
average of actual monthly numbers for the past six months, and the
predicted values for the following six months.

The low team predicts a smoothed sunspot number of 90 at the peak of
Cycle 24 in August, 2012.  The high team says Cycle 24 should peak
much earlier in September or October 2011, at 139.9.  And the
average of the two shows a peak of 113.1 in January, 2012.

In the past few days a sunspot has reappeared, with the emergence of
sunspot 986.  But it is way over on the Sun's west limb, and will
shortly pass from view.

The rest of this bulletin should look familiar.  The data at the
bottom covers the same March 6-12 time frame and all else is the
same, except the comments about a new forecast are deleted.

With just a few scattered sunspots in the past two weeks (February
28 to March 12), it isn't meaningful to ponder the change in weekly
averages.  There were just four days with sunspots during that time,
February 28, March 5-6 and March 10.

Regarding those two weeks, why do we report a week of data at the
end of this bulletin beginning on a Thursday and ending on
Wednesday?  Ed Tilton, W1HDQ (SK), a seasoned expert who wrote the
bulletin for several decades until early 1991, used a Monday through
Sunday reporting week, if I recall correctly, with a weekly bulletin
release every Monday morning.

With a change of authors 17 years ago, the bulletin shifted to a
Friday release, in time for increased activity on weekends.  We also
wanted to present the most recent data, and with a new bulletin
written every Thursday night, reporting data through Wednesday
seemed the safest choice, in case of any problem getting the
numbers.  At that time the world wide web was just about to be born,
and most of the data was obtained by dialing up sources over the
landline with a 2400 bps modem.

Back then, readers followed the bulletin from W1AW on HF via RTTY,
CW or SSB (where it is still transmitted today), or read it locally
via packet radio.  Today most readers see it on the web, or receive
it via email.  By the way, if any reader has an archive of bulletins
prior to 1995, I would like to hear from you via

Chuck Schram, W9UBT of Scottsdale, Arizona mentioned that this
bulletin hasn't identified recent sunspots as Cycle 23 or Cycle 24
spots.  That's true, but they were all Cycle 23 sunspots.  When we
see any Cycle 24 spots, you will read about it here.

Sunday, March 9 had the highest geomagnetic activity for the week,
with the Planetary A index at 25, and Alaska's College A index at
41.  But for many of us, unless we were trying to use HF over a
polar path, activity was moderate with the mid-latitude
Fredericksburg A index at 14.

For the short term, the US Air Force Space Weather Forecast Center
predicts sunspot and solar activity just as low and uneventful as it
was recently.  The next time a solar wind stream is expected to
drive geomagnetic activity to the same level as March 9 is March
26-28, the highest activity predicted for Thursday, March 27 with a
planetary A index of 25.  This would match last Sunday's activity,
except March 26 and 28 are expected to have higher geomagnetic
activity than March 8 and 10 did, with the planetary A index at 20
on both days.

You can read an interesting article about one of the teams in the
Air Force Space Weather Squadrons via  Over
the seven days from March 14 through 20 they predict a planetary A
index of 8, 5, 10, 10, 8, 8, and 5.  (The actual and predicted
values for those days have changed since this was written a few days
ago, to 13, 11, 5, 5, 5, 5, and 5).

Geophysical Institute Prague says to expect unsettled conditions for
March 14, quiet conditions on March 15, quiet to unsettled March
16-17, and quiet March 18-20.

While higher geomagnetic activity may degrade HF propagation,
especially over paths that cross high latitudes, last weekend's
activity brought welcome auroral propagation for VHF operators.

Paul Kiesel, K7CW (grid square CN87) wrote, "I just wanted to let
you know that we had a fairly nice radio aurora on 6 meters last
night. The Kiruna, Tromso and CARISMA magnetometers as well as the
NOAA POES Satellite all indicated excellent conditions when I
checked them at around 0415 UTC March 9. Sure enough, I heard KE7V
(in CN88, Paul's brother) right away and worked VE7DAY (CO70). VA6AN
(DO33), KL7NO (BP54) and VE6TA (DO33) followed soon after. The best
DX for us was K1TOL (FN44) at 0533 UTC. This was my best DX
buzz-mode contact on 6 meters to date, though I've worked Lefty
before on auroral-E. There may have been conditions on 2 meters, as
well, but when I checked, I heard nothing on that band. This is the
best aurora we've had in many months. Might be an indicator of good
things to come old-sol-wise".

Note the path from Paul to K1TOL was about 2,660 miles, and to
KL7NO, about 1,955 miles.

I asked Paul to tell us more about buzz-mode (signals bounced off
the auroral curtain) versus auroral-E propagation.

Paul comments, "Signals reflected back from the auroral curtain
typically are fluttery, distorted and hissy or gravelly sounding.
Sometimes SSB signals are hard to understand because the distortion
is so bad.  Auroral-E signals are clear, just like other sporadic-E
signals. The difference is that we know that the aurora is the prop
mode function, not the normally ionized E-layer. As far as working
K1TOL last night goes, it is unusual to work a station as far away
as he is via fluttery aurora. It's usually auroral-E that will get
you the real DX. I've worked only one other East Coast station via
buzz mode aurora. It was K7BV/1 in Connecticut a couple of years
ago. So, our working K1TOL via buzz mode was an unusual occurrence."

I think what Paul meant when he says "Auroral-E" is when the e-layer
is energized during an aurora.  It is only when signals are
propagated by bouncing off the aurora that they sound gravelly, but
signals propagated via e-layer during an aurora sound normal.  I
will check with him and report back in Thursday's bulletin.

Paul shared with us the magnetometers he mentioned in his first

Tromso (Norway) via, "I check the downward
blue trace deviation from horizontal. The lower, the more intense
the aurora. Solar wind Bz must be negative. (This relates to the
Interplanetary Magnetic Field orientation.  You can check the
current reading on the lower-left side of
A south-pointing IMF makes the earth vulnerable to solar wind, and
corresponds to a negative Bz)."

Kiruna (Sweden) via, "I check the downward
black trace deviation from horizontal. The lower, the more intense
the aurora. Solar wind Bz must be negative."

CARISMA (Canada) via, "Canadian reading from
a north-south line of magnetometers. Gives a decent indication of
real-time au conditions over North America."  It shows a green halo
when nothing special is going on.

NOAA POES via, "This is a good indicator of
intensity. POES satellite takes a reading on each orbit, so the
presentation represents a reading that may be up to 88 minutes old.
The more intense the conditions, the fatter and redder the au oval
is presented."

Finally, Terry McGleish, KC4TM of North Fort Meyers, Florida
recommends checking for 10 meter beacon
spotting reports. You can find details on Terry's own beacon at  He says there was a recent increase in reports
beginning March 11.

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 a detailed
explanation of the numbers used in this bulletin, see  An archive of past
propagation bulletins is at  Monthly
propagation charts between four USA regions and twelve overseas
locations are at

Sunspot numbers for March 6 through 12 were 12, 0, 0, 0, 12, 0, and
0 with a mean of 3.4.  10.7 cm flux was 70.3, 70.5, 69.8, 69.5,
70.3, 70.2, and 69.4 with a mean of 70.  Estimated planetary A
indices were 2, 3, 11, 25, 18, 12 and 14 with a mean of 12.1.
Estimated mid-latitude A indices were 2, 1, 6, 14, 12, 7 and 9, with
a mean of 7.3.


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