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ARRL Propagation Bulletin ARLP010 (2007)

ARLP010 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7RA
Seattle, WA  March 2, 2007
To all radio amateurs 

ARLP010 Propagation de K7RA

Sunspot numbers and solar flux both increased this week, but just
barely. Average daily sunspot numbers rose five points to 19.6,
while average daily solar flux rose one point to 75.8. Values are
expected to stay about the same over the next week. In fact, the
U.S. Air Force predicts an even 75 for solar flux over the next 30
days. Geomagnetic activity should remain quiet. Geophysical
Institute Prague agrees with outlook, predicting quiet to unsettled
conditions for today, March 2, quiet conditions on March 3-5, and
unsettled on March 6-7. The Air Force predicts 5 for the planetary A
index from March 2-5, 10 for March 6, and back to 5 after that.

You'll note when there is geomagnetic activity (see that often the
planetary A and K index will be higher than the mid-latitude
numbers. Since most of us live at middle latitudes, a quiet number
for the planetary A index means quiet conditions for us as well. On
the last day of February, a solar wind stream caused a rise in
geomagnetic activity. You can see on the above URL that the
planetary A index was 23, Alaska's College A index was 38, but the
mid-latitude A index was only 12.

In February we had low sunspot numbers, appropriate for the bottom
of the solar cycle. The average daily sunspot number for February
was just 17.3. The only months with lower average daily sunspot
numbers in the past year were October (14.7) and February 2006
(5.3). Monthly averages of daily sunspot numbers for February 2006
through February 2007 were 5.3, 21.3, 55.2, 39.6, 24.4, 22.6, 22.8,
25.2, 14.7, 31.5, 22.2, 28.2 and 17.3. Monthly averages of daily
solar flux for the same period were 76.5, 75.5, 88.9, 80.9, 76.5,
75.8, 79, 77.8, 74.3, 86.3, 84.4, 83.5 and 77.7.

This month just might be the bottom of the cycle. View the table at, and you'll see that
the predicted smoothed sunspot number for March 2007 is 11.3, and it
rises after that through the end of the year.

This weekend is the ARRL International DX SSB Contest, and
conditions will probably not be bad, at least no big geomagnetic
storms should occur. While there isn't much sunspot activity, our
local star isn't devoid of spots. Currently sunspot 944 faces us
from the center of the visible solar disk.

Eric Owen, KD4MZM of Sarasota, Florida sent a URL for a web page
devoted to 10-meter beacons at, Here you can
check loggings for 10-meter beacons, and leave your own feedback as
well for any you hear. There is also a list of links to individual
beacon web sites, and a beacon-chat area. Eric runs a beacon on
28.277 MHz.

In case you thought HF radio is no fun at the bottom of the solar
cycle, Aki, JA2UOZ, Aki, of Nagoya, Japan writes that he operates with
only one-half watt transmitter power and dipole antennas. Currently
he is trying for DXCC on 17 meters and higher at the bottom of the
solar cycle. He outlines his personal challenge at,, and some of his recent
contest logs at,

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 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,

Sunspot numbers for February 22 through 28 were 25, 22, 11, 12, 22,
23 and 22 with a mean of 19.6. 10.7 cm flux was 75.5, 75.1, 75.5,
76.6, 75.4, 74.8, and 75.8, with a mean of 75.5. Estimated planetary
A indices were 2, 2, 1, 3, 4, 12 and 23 with a mean of 6.7.
Estimated mid-latitude A indices were 2, 2, 2, 4, 4, 7 and 12, with
a mean of 4.7.


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