ARRL

ARRL Propagation Bulletin ARLP046 (2006)

SB PROP @ ARL $ARLP046
ARLP046 Propagation de K7RA

ZCZC AP46
QST de W1AW  
Propagation Forecast Bulletin 46  ARLP046
From Tad Cook, K7RA
Seattle, WA  November 10, 2006
To all radio amateurs 

SB PROP ARL ARLP046
ARLP046 Propagation de K7RA

Average daily sunspot numbers more than doubled this week over last,
up nearly 27 points to 46.3. While there were more sunspots, the
geomagnetic K index was 0, and on some days the A index was 0 as
well. Check out November 7-8 on,
http://www.sec.noaa.gov/ftpdir/indices/DGD.txt. A rare sight, with
nearly nothing but zeros straight across for two days, seemingly at
all latitudes. For the low end of the HF spectrum, what could be
better than a very quiet geomagnetic index and a long night?

That quiet period has come to an end. At 0600z on November 10, the
mid-latitude K index reported by WWV is 5, and the planetary K index
is 6, indicating a geomagnetic storm and a good night to observe
aurora. At the same time, sunspots 921 and 922 are leaving the
visible solar disc on the western limb, and sunspot 923 is emerging
on the eastern side.

On November 6, as sunspot 923 was about to emerge, it was throwing
off X-rays and a strong solar wind, but it was not yet aimed toward
earth. Astronomer Thomas Ashcraft is about 12 miles southeast of
Santa Fe, New Mexico, and has antennas aimed at the sun, with
receivers tuned to 18.7 and 22.2 MHz to detect radio noise. On
November 6 he recorded a particularly fast burst of solar radio
energy, and recorded it in stereo with the 18.7 MHz receiver feeding
one channel, and 22.2 MHz feeding the other. This produces an
interesting stereo effect, and you can hear it for yourself on his
web site, http://www.heliotown.com/Radio_Sun_Introduction.html.  He
recommends stereo headphones for maximum dramatic binaural effect.
This blast was from sunspot 923, which had not quite moved into
view. What would the effect have been if it was pointed toward us?
Interestingly, the geomagnetic field stayed very quiet for the next
few days.

Several readers, including Vince Varnas, K7ZH of Aloha, Oregon and
Jon Jones, N0JK of Wichita, Kansas commented on the report of 10
meter propagation from W0OGH in last week's bulletin. Both said that
this was more sporadic E propagation, and Jon noted that he worked
California on 6 meters around the same time.

Carl Luetzelschwab, K9LA, has a new article (in PDF format) just put
up on the Propagation section of the ARRL Technical Information
Service portion of the League web site. The title is, "The Precursor
Method of Predicting Solar Cycles," at,
http://www.arrl.org/tis/info/pdf/PrecursorMethod.pdf. He describes
one method for predicting an upcoming solar cycle, based on the
storminess (geomagnetically) of the period before the end of the
previous solar cycle.

Based on recent conditions, this would suggest a lower than normal
cycle 24. Currently, the solar minimum is still predicted for March
or April of 2007, only four to five months away. Carl isn't making
claims about the accuracy of such a prediction, but it is an
interesting illustration of the method.

Similarly, Gerry Fasse, W8GF of Warren, Michigan sent a link to a
2-year-old abstract from the American Geophysical Union about cycle
24 being small, and you can see the summary at,
http://www.agu.org/pubs/crossref/2005/2004GL021664.shtml.

By the way, Gerry is at the top of the DXCC Honor Roll, has both 160
and 6 meter DXCC in addition, and 5-Band WAZ.

Currently the predicted planetary A index for today, November 10,
through Tuesday, November 14 is 20, 10, 8, 8 and 5. Sunspot numbers
and solar flux should begin to taper off, reaching a short term
minimum around November 21-23, and becoming high again around
December 5-7.

Several readers sent in an article about the Hinode Solar Optical
Telescope, and some fantastic images of the sun expected from this
project. Read about it at,
http://science.nasa.gov/headlines/y2006/02nov_firstlight.htm?list5854.

Last week there was a typo at the beginning of the sunspot number
listing. For October 26-28, the sunspot numbers were 0, 14 and 28.

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/ .

Sunspot numbers for November 2 through 8 were 59, 57, 52, 62, 30, 26
and 38 with a mean of 46.3. 10.7 cm flux was 88.2, 87.4, 85.5, 84.7,
83.5, 87.1, and 86.4, with a mean of 86.1. Estimated planetary A
indices were 8, 8, 6, 5, 1, 0 and 1 with a mean of 4.1. Estimated
mid-latitude A indices were 6, 5, 4, 3, 1, 0 and 0, with a mean of
2.7.
NNNN
/EX