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17 November, 2007
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
replacement."
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:
http://sdo.gsfc.nasa.gov/.
SDO Mission Page:
http://sdo.gsfc.nasa.gov/mission/about.php.
SDO Instrument Page:
http://sdo.gsfc.nasa.gov/mission/instruments.php.
SDO EVE Overview Page:
http://lasp.colorado.edu/eve/instrument/eve_instrument.htm.
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 http://tinyurl.com/3yyok8.
The article mentions a site at, http://www.swpc.noaa.gov/ustec/
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,
http://sohowww.nascom.nasa.gov/
pickoftheweek/old/05oct2007.
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, k7ra@arrl.net.
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/.
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.
Source: The
American Radio Relay League
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reports can be found at:
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