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ARRL Propagation Bulletin ARLP003 (2009)

ARLP003 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 3  ARLP003
From Tad Cook, K7RA
Seattle, WA  January 16, 2009
To all radio amateurs 

ARLP003 Propagation de K7RA

A nice sunspot group, number 1010, appeared for five days from
Friday, January 9 through Tuesday, January 13.  Daily sunspot
numbers ranged from 11 to 20, and this one was another Cycle 24
appearance.  The Cycle 23 sunspots seem to be gone, while the new
solar Cycle 24 isn't picking up very quickly.

1010 was here for five days, following a whole solar rotation--27
days of no sunspots since 1009 was visible for just three days,
December 10-12.  Prior to that were 23 spotless days since seeing
sunspot 1008, visible for eight days from November 10-17.

This minimum looks longer and lower than the last solar minimum, but
there are many ways to slice the data.

For instance, on search the rather
cluttered home page and click the Sunspots tab to the right of Trend
Charts toward the upper right on the page, then inspect the bar
graph titled "Spotless Days vs. Cycle 23 Minimum," the second one
down from the top on the right.  Click on it to fill the page, and
see the comparison of spotless days per month for the period June
2007 through November 2008 with the earlier period June 1996 through
November 1997.

With all that red showing for spotless days in the recent period,
this certainly looks like a big difference between the recent period
and the one 11 years ago, but there is an inherent bias in comparing
May 2008 and May 1997, for instance.  This comparison might be valid
if solar cycles were precisely 11.0 years long, or in this case, 11
years from a cycle minimum to the next cycle minimum, but of course
this is not the case.  11 years is an approximation, and in fact if
you average all 23 of the previous solar cycles, the average number
is less than 11 years.

The problem becomes apparent if we look at the data and compare
spotless days for the five months prior to the beginning of this
graph, January through May.

It turns out that those months had a sixty-eight percent higher
number of spotless days back in 1996 than the same months 11 years
later.  From January 1, 2007 through May 31, 2007 there were 40
spotless days.  But January 1, 1996 through May 31, 1996 had a total
of 67 spotless days.

Data that is uncertain is in August 2008, which is listed with all
spotless days. But August 21-22 there was a brief sunspot
appearance, although it wasn't widely reported because there was
some speculation regarding whether it was big enough to be counted
as a sunspot.  Check and on the
archives area at the right side of the page, change the date to
August 21, 2008, and note that under the Daily Sun on the left
margin, it shows the daily sunspot number as 11.  To the right of
the daily Sun you can click on the photograph under the heading New
Sunspots for a closer look.

Now check August 22, and see the same sunspot number 11.

It is easy to inspect this data and make comparisons if you download
the Solar Data Plotting utility mentioned in our first bulletin of
this year, Propagation Forecast Bulletin ARLP001, at  The GRAPH.dat file
for this program has sunspot and solar flux numbers since the start
of 1989, and if you copy it into your documents folder and rename
the file to graph.doc, you can page through it easily with a word
processor.  You can also take this file and load it into a
spreadsheet program.

At least with our quiet Sun the geomagnetic indices continue to stay

Geophysical Institute Prague predicts quiet days from January 16-22,
except January 18 to be unsettled, and January 19 at quiet to
unsettled.  NOAA Space Weather Prediction Center along with the U.S.
Air Force predict quiet conditions with a planetary A index of five
for the rest of January, except 8 on January 19, 10 and 8 on January
27-28, and 8 again on January 30.

Last week's propagation forecast bulletin mentioned the STEREO
mission, and how to find out what the current satellite positions
were, relative to earth and the Sun.  John Fors, WD7Z of Capulin,
New Mexico sent a link to a page which allows you to see the
positions for any date or time at,

John said that from February 2011 onward, STEREO should get a
detailed simultaneous view of all sides of the Sun.  This will give
a precise reading of activity soon to rotate into view.

Currently it shows the two satellites at nearly a 90 degree angle
from each other.  Six months from now the angle will be 104 degrees
and a year from now it should be at 134 degrees.  Two years from now
they will be nearly opposite each other at 177.6 degrees.  The last
date I can generate the listing of angles for is January 21, 2012
when STEREO-B is 113.669 degrees relative to earth, and STEREO-A is
107.583 degrees relative to earth.  Beyond that date users can
continue to generate the visual plots, and ideally the two
satellites and earth would all be ultimately positioned 120 degrees
relative to each other for maximum coverage.

No 6 meter reports from North America this week, but there was one
from Spain.  Joaquin Montoya, EA2CCG reported that on January 12 he
worked OE1SOW in Vienna, followed by another Austrian, then Poland,
Germany, Croatia, Slovak Republic, and Slovenia.

He used a Moxon antenna (see that was broken
during a recent ice storm and hanging from the tower, and signals
were S5-S7 with QSB.

Joaquin said 10 meters was open on the same day, and that he could
hear European beacons.  He worked the TS7C expedition on Kerkennah
Island in Tunisia on 10 meters that morning.

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 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

Instructions for starting or ending email distribution of this
bulletin are at

Sunspot numbers for January 8 through 14 were 0, 14, 17, 20, 12, 11,
and 0 with a mean of 10.6.  10.7 cm flux was 68.7, 69.7, 70.9, 70,
69.3, 70.5, and 71.2 with a mean of 70.  Estimated planetary A
indices were 3, 4, 4, 2, 0, 3 and 5 with a mean of 3.  Estimated
mid-latitude A indices were 2, 4, 2, 1, 0, 2 and 6 with a mean of


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