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ARRL Propagation Bulletin ARLP047 (2007)

ARLP047 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 47  ARLP047
From Tad Cook, K7RA
Seattle, WA  November 16, 2007
To all radio amateurs 

ARLP047 Propagation de K7RA

Another quiet week, but strangely, like the previous week there was
just a single sunspot appearing for one day, and it was also on a
Tuesday.  Just like the previous week, the daily sunspot number was
11, and then it went back to 0 when the spot disappeared.  No spots
expected in the near future.

Geomagnetic indices have been quiet, but may become unsettled in the
near term.  Geophysical Institute Prague predicts quiet to unsettled
conditions for November 16, quiet November 17, quiet to unsettled
November 18, quiet November 19, quiet to unsettled November 20,
unsettled to active November 21, and unsettled November 22.  The
NOAA Space Weather Prediction Center sees a planetary A index of 10
for November 16, 5 for November 17-19, 10 for November 20, 15 for
November 21, and 10 for November 22.

Many interesting emails this week, and one came from Bob Marston,
K6TR of Fremont, California.  He mentioned the theory about magnetic
polarity of sunspots, and how we expect them to shift as we move
into a new cycle.  But some time back a reverse polarity spot
appeared, and was hailed by some as the first spot of Cycle 24, but
it turned out this wasn't the case.  Bob says about 3 percent of the
spots in any cycle are rogue spots with reverse orientation.  What
will be significant is when we start to see spots appearing away
from the equator.

Bob continued, "The second topic I want to address is the item Carl
Luetzelschwab, K9LA, brought up referencing his communication with
Mike Keane, K1MK. The 30.4 nm resonance line is the best indicator
for gauging the state of ionization of the ionosphere. What I would
like to point out is the future of the Solar and Heliospheric
Observatory (SOHO). SOHO was originally intended to last a few years
when it was launched in 1995 and has lasted four times as long.  It
has done yeoman's service and done more to increase man's
understanding of the Sun than any other space-based solar
observatory. But it is getting long in the tooth and in need of

He goes on to say, "To that end, NASA will launch a replacement
satellite observatory called the Solar Dynamics Observatory (SDO).
It is currently undergoing final assembly at NASA's Goddard Space
Flight Center near Greenbelt, Maryland. Launch date is currently
scheduled for no earlier than December 1, 2008 and it is expected to
be operational within 90 days of launch.  "The assembly team is in
the early stages of construction with the first of three instruments
delivered last month. That instrument is the Extreme Ultraviolet
Variability Experiment (EVE). It is the analogous instrument to the
SEM on SOHO. When you check out the specs of the new instrument, it
is readily apparent the jump in capability the new instrument offers
over the SEM on SOHO."

He continues, "Unlike SOHO, SDO will be placed into a geosynchronous
orbit around the Earth.  That is to provide better communications to
handle the higher data rate coming from the new satellite. Images
that are updated every five minutes on SOHO will be updated once a
second on SDO. SOHO orbits the Sun at a Lagrange point, one million
miles from Earth. This provides uninterrupted observation of the
Sun.  SDO will have two 90 day periods per year where its
observations will be interrupted for a maximum of 72 minutes while
it passes behind the Earth."

Bob ends by saying, "You might want to remind your readers,
especially the younger ones, that while conditions may be
challenging right now they will get better.  And the set of new
tools coming online in the next year and a half will provide us with
the information to exploit F layer ionospheric propagation like
never before, regardless of what the sunspot count at the peak of
Cycle 24."

SDO Home Page:

SDO Mission Page:

SDO Instrument Page:

SDO EVE Overview Page:

Thanks, Bob for the great information.

This week several people wrote in about an article from NASA about
ion plumes, titled "Strange Space Weather Over Africa."  You can
read it at

The article mentions a site at, in
which users can look at changing electron content in the ionosphere
over North America.  Note that you can look at animations of the
shifting patterns of electron content over 24 hours.

Jose Nunes, CT1BOH of Lisbon, Portugal sent in a link to an article
about the cycle minimum at,

Next week we hope to have more details on some unusual long path
propagation on 80 meters from the West Coast to South Africa, while
both ends of the path were in daylight.  Don't forget ARRL Phone
Sweepstakes this weekend.  Conditions should be fine for this
domestic contest.

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 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 November 8 through 14 were 0, 0, 0, 0, 0, 11 and
0 with a mean of 1.6.  10.7 cm flux was 69.7, 69.5, 69.8, 69, 69.7,
69.9, and 70.4 with a mean of 69.7.  Estimated planetary A indices
were 3, 2, 3, 1, 2, 8 and 9 with a mean of 4 Estimated mid-latitude
A indices were 3, 2, 2, 1, 2, 7 and 9, with a mean of 3.7.


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