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ARRL Propagation Bulletin ARLP014 (2009)

ARLP014 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 14  ARLP014
From Tad Cook, K7RA
Seattle, WA  April 3, 2009
To all radio amateurs 

ARLP014 Propagation de K7RA

Our Sun is in the news again, unfortunately not due to any hoped for
activity, but for the eerie quiet instead.  The Sun is surprisingly
calm by several measurements -- including the large number of
spotless days -- average 10.7 cm solar flux, and low solar wind

According to an April 1 release from NASA that I wish was just an
April Fool's joke, we are witnessing a 50-year low in solar wind
pressure -- a 20-percent drop since the mid 1990s.  Of course the
advantage to this is geomagnetic storms are very rare.  But that is
a disadvantage for VHF operators who enjoy using aurora to propagate
radio waves.

The news release at claims that 10.7 cm
solar flux is at a 55-year low, although this figure has only been
tracked for the past 65 or so years.  They also tell us that 2008
had more spotless days than any year since 1913 (see

In this bulletin we have calculated a running 3-month average
sunspot number, and the average for January through March --
centered on February -- at 2.1 was the lowest 3-month average since
July and August of 2008.

Here are the averages since January 2007.

Jan 07 22.7
Feb 07 18.5
Mar 07 11.2
Apr 07 12.2
May 07 15.8
Jun 07 18.7
Jul 07 15.4
Aug 07 10.2
Sep 07  5.4
Oct 07  3.0
Nov 07  6.9
Dec 07  8.1
Jan 08  8.5
Feb 08  8.4
Mar 08  8.4
Apr 08  8.9
May 08  5.0
Jun 08  3.7
Jul 08  2.0
Aug 08  1.1
Sep 08  2.5
Oct 08  4.5
Nov 08  4.4
Dec 08  3.7
Jan 09  2.3
Feb 09  2.1

Using this table, we have been fooled before, thinking that an
up-trend would continue.  Take a look at the periods centered on
October 2007 or August 2008.

The first Propagation Forecast bulletin of 2008
( noted that one
year prior we commented that 2007 would likely see the transition
from Cycle 23 to 24.  Then in the fifth bulletin of last year
( we saw that uptick
in the 3-month moving average, suggesting that the new cycle was
commencing.  The same bulletin noted that four years prior to that,
in 2004 a reader asked if we might be at the end of Cycle 23.

We've looked at various predictions for the next cycle, and that
same NASA article referenced above has a plot of the various
predicted maxima at  Quite a range!  At
one time we were excited by the prediction of Dikpati et al, because
it foretold a robust Cycle 24.  But note in the chart (that you can
zoom in on by clicking) there were actually four predictions more
optimistic that her team's projection.  My favorite, since it is the
most wildly optimistic, is the 2005 forecast by Horstman, which
crunched data from the last five solar cycles, starting with 19, of
course, for a sunspot peak of 185 in 2010 or 2011.

Right now there are no sunspots, but the 10.7 cm solar flux is up a
bit lately.  The latest prediction has the usual quiet planetary A
index at 8 for April 3-4, then back to 5, then 15 and 10 for April
9-10.  Predicted solar flux is 71 for April 3-9, then back to 70 for
April 10-22, then to 72 for April 23 and into May.

Recent mail indicates operators are still enjoying the HF bands,
even without sunspots.  Matthew Chambers, W1JEQ of Newark, Missouri
says he had fun working HI3TEJ, ZW5B, YW4D, PY6HD, and several U.S.
stations in a recent DX contest, using just a barefoot transceiver
and a 20 meter monoband mobile whip attached to a fire escape.  He
notes, "If this is what zero sunspots can sound like then I can't
wait to hear the bands with sunspots!"

Tim Hickman, N3JON of Timonium, Maryland wrote, "After a more quiet
than normal week, if that is even possible, the bands were popping
late afternoon and early evening on Thursday April 2 2009.  On 20
meters strong signals from CN8KD at 2100 show up in Maryland then
VKs and JA start showing up on 20 meters then 2 hours later AG1AB is
working the east cost with solid 59s on 40 meters then on the
spotters net reports start showing up of DX on 10 meters which I can
hear but not well enough to work.  It was nice to see the bands come
alive at least for a moment - we all can hope this is the harbinger
of things to come!"

Russ Ward. W4NI of Nashville, Tennessee likes the new book
"Midlatitude Ionospheric Dynamics and Disturbances" by Kintner and
Coster, although he says it is very advanced and notes it is "not
for the unmotivated.  I noticed also that the book is very

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

Instructions for starting or ending email distribution of this
bulletin are at

Sunspot numbers for March 26 through April 1 were 0, 0, 0, 0, 0, 0,
and 0 with a mean of 0.  10.7 cm flux was 69.1, 71.6, 70.6, 70.9,
70.9, 71.2, and 70.8 with a mean of 70.7.  Estimated planetary A
indices were 7, 4, 4, 5, 4, 4 and 4 with a mean of 4.6.  Estimated
mid-latitude A indices were 6, 2, 2, 4, 3, 2 and 3 with a mean of


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