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ARRL Propagation Bulletin ARLP039 (2006)

ARLP039 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
From Tad Cook, K7RA
Seattle, WA  September 22, 2006
To all radio amateurs 

ARLP039 Propagation de K7RA

Average daily sunspot numbers this week were down nearly 31 points
to 13.4, and average daily solar flux declined over 8 points to 77.
Sunday through Thursday of this week, the sunspot number was 11 on
all five days.  Sunspot activity should remain low.

This week a coronal wind stream caused a geomagnetic disturbance
centered on September 18.  A week ago, on Friday, September 15,
geomagnetic conditions were very stable.  The mid-latitude K index
throughout the day was zero on all eight readings, and so the
mid-latitude A index was also zero.  Even the high latitude college
A index near Fairbanks, Alaska was zero that day.

Due to a recurring coronal hole, we may see a rise in geomagnetic
activity this weekend, with the planetary A index predicted at a low
of 5 on Friday, then rising to 20 on Saturday, September 23.

Today a group of satellites should be launched that will give
3-dimensional views of solar flares.  The plan is to view flares
from two satellites, spaced far enough apart to give stereo vision.
Jerry Reimer sent a link to an article about this in Britain's
Sunday Times. Read it at

Yvone Dubois, KE7HTQ of Phoenix asks, ''Where can I find propagation
charts old style, like they used to be published in QST for

The charts have moved from the magazine to the web.  Find them 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 .

Sunspot numbers for September 14 through 20 were 25, 12, 13, 11, 11,
11 and 11 with a mean of 13.4. 10.7 cm flux was 82.8, 80.1, 79.2,
78, 74.4, 73.4, and 70.9, with a mean of 77. Estimated planetary A
indices were 6, 3, 3, 16, 24, 12 and 5 with a mean of 9.9. Estimated
mid-latitude A indices were 4, 0, 1, 9, 16, 8 and 3, with a mean of


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