ARRL

ARRL Propagation Bulletin ARLP025 (2009)

SB PROP @ ARL $ARLP025
ARLP025 Propagation de K7RA

ZCZC AP25
QST de W1AW  
Propagation Forecast Bulletin 25  ARLP025
From Tad Cook, K7RA
Seattle, WA  June 19, 2009
To all radio amateurs 

SB PROP ARL ARLP025
ARLP025 Propagation de K7RA

This week's bulletin was written by Carl Luetzelschwab, K9LA.  Carl
is filling in for your regular reporter Tad Cook, K7RA.

Silent Key - I was saddened to read that Jim Tabor KU5S passed away
on May 27.  Jim was the driving force behind Kangaroo Tabor
Software, which offered propagation prediction programs such as
CapMAN and WinCAP Wizard, programs to help monitor the NCDXF/IARU
beacons, and several other propagation-related packages.  Jim also
contributed propagation software to the CD-ROM bundled with the ARRL
Antenna Book.  I personally enjoyed many e-mail exchanges and
several QSOs with Jim, talking about various propagation and
ionospheric issues.

Summary for the Week - I bet you have this memorized: ''Solar
activity was very low throughout the reporting period, and
geomagnetic field activity was at quiet levels during most of the
reporting period.''  Enough said?

This Solar Minimum - The first sunspot region of Cycle 24 occurred
on January 4, 2008.  Since then, though, Cycle 24 spots have been
few and far between.  A good summary of this solar minimum can be
made in two statements.  The first statement is that the duration of
this solar minimum is unusual compared to the other solar minimums
in our lifetime.  That's because from the minimum between Cycle 17
and 18 onward, solar minimums have been roughly two years.  Thus
we've only been exposed to ''short'' solar minimum periods.  A look at
all history, though, shows a different story, and brings us to the
second statement.  This solar minimum, which is going on three
years, is pretty much average in duration compared to all history.
What this all says is the Sun has been highly variable throughout
recorded history.

Noctilucent Clouds Return - As reported at spaceweather.com on June
1, the first noctilucent clouds (NLC) of the 2009 season were
sighted over Russia on May 27.  NLCs typically appear about 20 days
prior to the summer solstice, increase quickly to a high summer
level, and then disappear about 50 days after the summer solstice.
These clouds are mostly a high latitude phenomenon, and are believed
to be composed of ice crystals.  VHF radars see very strong echoes
from these clouds, and since they are at mesospheric heights (80 to
90 km), they are also known as polar mesosphere summer echoes
(PMSE).  These clouds are hypothesized by JE1BMJ and others to be
responsible for 6m propagation across high latitudes (for example,
from the East Coast of North America to Japan) during the northern
hemisphere summer.  This mode of propagation has been dubbed Summer
Solstice Short-path Propagation (SSSP).  Check out page 34 of the
February 2009 issue of WorldRadio Online (available free at
www.cq-amateur-radio.com/wr_back_issues.html)
for a general discussion of PMSE and SSSP and for references in the
technical literature.  To reiterate, SSSP is still just a theory,
but the occurrences of QSOs appear to match the occurrence pattern
of PMSE.

Getting Ready for Glorioso - Beginning on July 9 and continuing
through July 28, a French team expects to activate this extremely
rare DXCC entity (it's in the Top 5 in the Most Wanted Survey as
listed in the January/February 2009 issue of The DX Magazine).
Glorioso is located in the Indian Ocean near the northern tip of
Madagascar, and enjoys higher-than-usual MUFs (maximum usable
frequencies) even at solar minimum due to the robust equatorial
ionosphere.  Unfortunately the North American end of the path will
suffer from low MUFs due to a combination of solar minimum and a
summer month.  The result of this is that 15, 12, and 10 meters will
likely not produce many QSOs between Glorioso and North America.  My
recommendation is to concentrate your efforts on 40, 30, 20, and 17
meters.  And if you need Glorioso for an all-time new one for DXCC,
be sure to work this DXpedition - it will probably be quite a while
until it is again activated.

Cycle 24 Predictions - If you dig through the technical literature,
you'll discover that there are more than 50 predictions for Cycle
24.  They range from a low smoothed sunspot number of 40 to a high
of 185.  Why are there so many predictions?  That's a simple
question to answer - solar scientists do not fully understand the
process that generates sunspots, and thus many different methods
have been used to make a prediction.  Does this mean they're
guessing and should be admonished for not being correct?  I
personally don't think so.  What we're seeing is the scientific
process being used.  A prediction is made using a certain method,
and Cycle 24's progress (or lack of progress) allows scientists a
means to test their theory.  That's how science works when we don't
understand something.  Will we ever figure this out?  I can't answer
that question, but I recently read an interesting NASA Headline News
story (science.nasa.gov/headlines/y2009/17jun_jetstream.htm?list45339)
saying scientists announced that ''a jet stream deep inside the Sun
is migrating slower than usual through the star's interior, giving
rise to the lack of sunspots.''  Perhaps this will be an important
clue to help our understanding of the sunspot process.

For more information concerning radio propagation, see the ARRL
Technical Information Service at
http://www.arrl.org/tis/info/propagation.html.  For a detailed
explanation of the numbers used in this bulletin, see
http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
propagation bulletins is at http://www.arrl.org/w1aw/prop/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at http://www.arrl.org/qst/propcharts/.

Instructions for starting or ending email distribution of this
bulletin are at http://www.arrl.org/w1aw.html#email.

Sunspot numbers for June 11 through 17 were 0, 12, 0, 0, 0, 0, and
11 with a mean of 3.3.  10.7 cm flux was 69.3, 69, 68.2, 68.1, 67.4,
68.3, and 67.8 with a mean of 68.3.  Estimated planetary A indices
were 3, 2, 4, 6, 4, 3 and 3 with a mean of 3.6.  Estimated
mid-latitude A indices were 2, 1, 3, 4, 4, 4 and 1 with a mean of
2.7.
NNNN
/EX