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15 December, 2007
ARLP052
Sunspot 978 made a strong showing this week, and daily sunspot numbers
are up as a result. The average daily sunspot number for this week rose
over 25 points to 36.7, and average daily solar flux rose over 14 points
to 87.2.
The sunspot numbers on December 9-11 were 42, 43 and 44. Sunspot numbers
haven't been nearly this high since July 14-15 of 2007, when it was 41
both days. The daily sunspot number hasn't been higher since June 2 to
June 8 of this
year, when it was 45, 58, 58, 63, 47, 59 and 51.
You can make your own animation of the emergence and movement of sunspot
978 with photos on http://www.spaceweather.com.
Just click on http://snurl.com/ss978
and in the URL field change /06dec07/ to /07dec07/, hit the Enter key,
then change it to /08dec07/, hit Enter, and repeat until you reach /13dec07/
(14dec07 will probably also work by the time you read this bulletin).
Now you can use your browser's forward and back keys to animate the sunspot
and watch it move. It is a big sunspot.
Geomagnetic activity was very low, although it was slightly
unsettled around December 11-12 at northern latitudes. But take a look
at the table at, http://snurl.com/geokna.
Note the absence of any geomagnetic activity in the far north, represented
by the strings of zeros for Alaska's College A and K index from November
30 to December 9. The K index is measured every three hours, or eight
times per day. Notice in the 64 readings from 1200z December 1 to 0900z
December 9, the College K index rose from 0 to 1 only twice.
Tim Goeppinger, K6GEP of Orange, California wondered why, with the higher
sunspot numbers, he didn't see better propagation last weekend in the
ARRL 10 Meter Contest. Recently this bulletin mentioned unexpected 10
meter propagation when there were no sunspots. This may be a case where
this week's sunspot activity wasn't enough to support F layer propagation
at 28 MHz, but perhaps recent 10 meter DX was actually supported by sporadic
E propagation.
The US Air Force and the NOAA Space Weather Prediction Center forecast
solar flux at 95 for December 14-16, and 90 on December 17-19. This suggests
a possible continuation of recent sunspot activity, because sunspot numbers
this week were 39-44 while solar flux was 89-94.
They also predict a planetary A index for December 14-20 at 5, 5, 10,
20, 15, 15 and 10, so expect unsettled to active geomagnetic conditions
on Monday, December 17. Geophysical Institute Prague predicts quiet conditions
December 14-16, active December 17, and unsettled December 18-20.
This week there are a slew of new articles from various sources on solar
science and Hinode. Rather than give you a multiple links, let's try something
new. Copy and paste or just type http://snurl.com/sunmem1
to your web browser's URL field and hit the Enter key to read the first
article. For the second, paste again, but change sunmem1 to sunmem2. Keep
up that process through sunmem7 to read all seven articles.
Next week is Winter Solstice in the Northern Hemisphere, on
Saturday, December 22. After that the hours of daylight will
gradually grow longer, and the increased sunlight will improve propagation
on the higher bands. Three months away is the Spring Equinox, and if we
have more sunspots by then, so much the better.
In the interim, we can take advantage of the long nights and low geomagnetic
activity to enjoy the low bands, 160 and 80 meters.
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 December 6 through 12 were 29, 24, 36, 42, 43, 44
and 39 with a mean of 36.7. 10.7 cm flux was 78.2, 82.2, 86.9, 88.9, 86.9,
93.4, and 93.9 with a mean of 87.2. Estimated planetary A indices were
1, 1, 0, 2, 8, 12 and 7 with a mean of 4.4. Estimated mid-latitude A indices
were 1, 0, 1, 1, 5, 9 and 7, with a mean of 3.4.
Source: The
American Radio Relay League
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• All propagation
reports can be found at:
http://www.southgatearc.org/propagation
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