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ARRL Propagation Bulletin ARLP050 (2010)

ARLP050 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 50  ARLP050
From Tad Cook, K7RA
Seattle, WA  December 17, 2010
To all radio amateurs 

ARLP050 Propagation de K7RA

Average daily sunspot numbers for this week declined over seven
points to 27.6 from the previous week, December 2-8.  Solar flux was
about the same as last week, the average up less than a point.

Predicted planetary A index for the next ten days, December 17-26 is
5, 8, 8, 5, 5, 8, 5, 5, 7 and 5.  Solar flux for the same days is
predicted at 82, 80, 80, 78, 78, 78, 78, 78, 88 and 88.  Flux values
are expected to rise to 90 by December 29 through January 1.

Geophysical Institute Prague predicts quiet to unsettled conditions
for December 17, unsettled December 18-19, quiet to unsettled
December 20, and quiet December 21-23.

A week ago two sunspot groups were visible, 1131 and 1133.  The last
day 1131 could be seen was December 14, after which it rotated out
of view.  It first appeared on December 2, and was a big sunspot
group.  Comparable sized groups were 1108 on September 16-28, 1109
on September 21 to October 4, and 1117 on October 19 through
November 1.  All other recent groups have been much smaller.

Sunspot group 1133 is rotating out of view, visible for 13 days
after arrival on December 4.  The sun would be spotless, but a new
sunspot group 1135 emerged on Thursday, December 16, when the daily
sunspot number rose from 11 (the minimum non-zero value, on
Wednesday) to 23.

John Kountz, WO1S of Laguna Beach, California (also T6EE when he was
in Kabul) sent some info on a new piece of free software from NASA
called "JHelioviewer."  You can get more info at on this visualization software for examining
images from the Solar Dynamic Observatory (SDO).  John and I have
both installed this software, but haven't yet figured out where to
get the SDO data.  With it, we should be able to examine any images
from the SDO project, which was launched on February 11, 2010.  For
instance, it might be interesting to look at images of sunspot group
1108 by grabbing images of the Sun from September 16-28.

There is an online version of the program at  You can enter a date, then choose an
interval in the Time-Step field.  Setting it to 12 Hours and
clicking on the arrow to the right of that field gives a nice
twice-per-day solar image that shows emergence of activity and
tracks it across the earth-facing side of the sun.

Go to to look
at quarterly sunspot data, and pick a period with high sunspot
numbers.  For instance, stepping through 12 hour increments
beginning October 16 shows quite a lot of interesting activity. Take
the interval down to 15 minute increments, and you can examine a
great deal of detail as prominences emerge and decay.

Scott Bidstrup, TI3/W7RI and several other readers sent references
to an article at about
a solar event on August 1, and how it was observed by the SDO and
STEREO projects.  At
you can see the resulting A and K indices several days later.  While
this was a fairly large event, what made it so interesting this time
were all the instruments in place for observing it.

Pete Heins, N6ZE of Thousand Oaks, California is in grid square
DM04ne where he operates 6 meters.  He didn't say if he was using
SSB or CW, but on December 14 for about 90 minutes he worked quite a
bit of E-skip.

He first heard K0GU (DN70) at 0250z while mobile.  A visit to shows us an image of the impressive
antenna array that K0GU was probably using when Pete heard him.  No
doubt hearing E-skip sent Pete home, where 9 minutes later at 0259z
he worked W7GNE (DM43), then W0GMO (DN70) at 0306z, AB7OI (DN41) at
0413z, WA7YAZ (DN40) at 0422z, and NJ7A (DN30) at 0437z. Arizona,
Colorado and Utah. Not bad!

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 an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at  Find more good
information and tutorials on propagation at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for December 9 through 15 were 22, 33, 25, 23, 46,
33, and 11, with a mean of 27.6. 10.7 cm flux was 86.8, 88.4, 86.9,
89.4, 87.7, 90.3 and 86.9 with a mean of 88.1. Estimated planetary A
indices were 2, 0, 1, 4, 5, 11 and 9 with a mean of 4.6. Estimated
mid-latitude A indices were 0, 0, 1, 3, 5, 10 and 8 with a mean of


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