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ARRL Propagation Bulletin ARLP011 (2008)

ARLP011 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 11  ARLP011
From Tad Cook, K7RA
Seattle, WA  March 14, 2008
To all radio amateurs 

ARLP011 Propagation de K7RA

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.

A new forecast is out regarding progress between sunspot Cycles 23
and 24.  You may recall that the committee of scientists who make a
group forecast of future sunspot activity for the NOAA Space Weather
Prediction Center were unable to reach a consensus last year, evenly
split between those who think the next solar cycle will be weak, and
another group which sees a stronger solar cycle.

I will refer to the weak cycle predictors as pessimists, and strong
cycle forecasters as optimists.  While these characterizations may
not be appropriate for scientists who presumably have no preference
either way, for amateur radio operators, the high cycle prediction
is no doubt the optimistic choice.

The previous prediction appeared in the January 2, 2008, issue 1687
of the Preliminary Report and Forecast available in PDF format from

Note on page 8 in the table of predicted smoothed sunspot numbers
that the optimistic faction predicts a sunspot minimum of 4 centered
around December 2007 through April 2008.  The pessimistic projection
is for a smoothed sunspot number minimum of 3 from January through
April 2008.

Now compare this with the prediction ten weeks later on page 9 of
issue 1697 from this week, available at,
See how the pessimists are now calling for a much longer and lower
solar minimum lasting over a year, from November 2007 through
December 2008.  But according to the optimists, the solar minimum
has already passed, with a smoothed sunspot number of 6 in August
and September 2007. (This generally agrees with our 3-month averages
of daily numbers, presented in last week's Propagation Forecast
Bulletin ARLP010 linked from

Note there is no split in the value for August 2007.  This is
because 6 is the known smoothed sunspot number for that month, not a
prediction.  A year of daily sunspot numbers is required to
calculate the smoothed value, and all of the values from
mid-February 2007 through mid-February 2008 (a whole year with
August in the middle) are known.  In fact, enough sunspot data will
be known this weekend to fix the smoothed sunspot number for
September of last year.

Now look at even better news for sunspot fans.  See how the
predictions for the peak of the next solar cycle have shifted, and
both factions see Cycle 24 peaking much higher than they did ten
weeks earlier.

In issue 1687, pessimists predicted a peak between May and October
2012 of only 90, but now in issue 1697 we see a much higher and
earlier peak at 124 from August through December 2011, only three
and a half years from now.  The optimists and pessimists now agree
on the timing of the peak, and optimists have upped their peak value
prediction from 140 to 154. (Access all recent weekly issues at,

Of course, with only 23 cycles of data to examine, sunspot cycle
prediction is still a young science.  But new tools unavailable in
past decades no doubt have advanced the art.

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.

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.

He writes, "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."

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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