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ARRL Propagation Bulletin ARLP002 (2009)

ARLP002 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 2  ARLP002
From Tad Cook, K7RA
Seattle, WA  January 9, 2009
To all radio amateurs 

ARLP002 Propagation de K7RA

In the past couple of weeks we hoped for a return of sunspots
because activity was detected on the side of the Sun opposite from
earth.  The Sun rotates relative to earth about every 27-28 days
(although the rotation varies somewhat with latitude), and so unless
it fades quickly away, far side activity may come into view.  Until
fairly recently astrophysicists could only guess on far side events,
but some modern methods have extended the view.

Helioseismology is the study of pressure waves in the Sun, and can
be used to detect sunspots on the far side by looking for magnetic
variations corresponding to sunspots.  Pressure waves bounce around
inside the Sun, and the echoes change when they reflect off of
magnetically complex areas.

Stanford University has a page devoted to acoustic imaging of the
Sun's far side at,, and Wikipedia
has a page at,

NASA's STEREO Mission (Solar TErrestrial RElations Observatory) can
provide views around the sides of the Sun, because it employs two
identical satellite observatories, one leading earth's orbit, and
the other trailing.  It can also provide three-dimensional images.

For details, see the NASA STEREO mission page at, and also
check  You can
see the satellite's current positions at,

Herbie Feichtinger, DC1YB wanted everyone to take a look at the
STEREO images at, that
show both current ahead and behind images.  Also check out his
projects on his web site at,

Besides the spot indications from the far side, the NOAA/USAF daily
forecast predicted a rise in daily solar flux, which could correlate
with sunspot appearance.

On the site,
you can check the daily forecasts going back three weeks.  Note on
December 23 they first predicted a rise of solar flux to 71, running
from December 31 through January 5.  The next day, December 24,
their prediction changed to December 27 through January 5.  This
remained until the December 29 forecast, when it changed to 70 for
December 30 through January 7, and below 70 after that.  The latest
forecast on January 8 had solar flux remaining below 70 until
January 15, then rising to 70 for January 16 through February 5, but
never rising above 70.

On Wednesday, January 7 a sunspot appeared very briefly in the lower
right portion of the Sun's image.  It was so brief that NOAA did not
record it at, but reported a sunspot number of 11 for the day, and
the magnetic polarity was consistent with a new Cycle 24 spot.

Today on January 9 there is another Cycle 24 appearance, this time
on the upper left of the image.

See it at,

Last week's Propagation Forecast Bulletin ARLP001 reported that the
ionosphere is now at a lower elevation than in the past, but Carl
Luetzelschwab, K9LA wrote in suggesting that this isn't really true,
and our misunderstanding is probably due to some poor science
reporting. The data reported is only accurate for equatorial

An explanation is on Carl's web site,  Just click on "Timely Topics"
toward the top, then the January 3 report, titled "Is the ionosphere
really lower?"

Michael Mona, KD0ZW, of Clive, Iowa wrote about his QRP experiences,
and said that even with no sunspots he is having fun running 5
watts, and only batteries powered by a solar cell. Read about it on
his web site at,

Flavio Archangelo, PY2ZX, wrote to tell us about an interesting
experiment he is participating in with the Japy DX Group.  They are
traveling north in Brazil to Bahia to experiment with transatlantic
tropospheric ducting propagation with Africa.  An English language
web page is at, and is in Portuguese.  You can paste
that last URL into a translation tool at, under the Translate a Web
Page heading.  Just select Portuguese for the first language option,
and English or any other language for the second option.

Of course, it is currently several weeks into Summer on that side of
the equator.

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 1 through 7 were 0, 0, 0, 0, 0, 0, and 0
with a mean of 0.  10.7 cm flux was 68.9, 69.9, 69.5, 68.8, 69.2,
68.7, and 69 with a mean of 69.1.  Estimated planetary A indices
were 6, 3, 9, 4, 4, 3 and 3 with a mean of 4.6.  Estimated
mid-latitude A indices were 5, 3, 8, 5, 3, 2 and 1 with a mean of


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