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QST de W1AW  
Propagation Forecast Bulletin 11  ARLP011
>From Tad Cook, K7RA
Seattle, WA  March 14, 2003
To all radio amateurs 

SB PROP ARL ARLP011
ARLP011 Propagation de K7RA

Average daily solar flux and sunspot numbers were up again this
week. Average daily sunspot numbers, which were up nearly 50 points
last week compared to the previous week, this week rose nearly 70
points compared to last week. Average daily solar flux was up 30
points last week and over 7 points this week. Solar flux is expected
to decline to just above 100 from March 20-24, around the time of
the solar equinox.

There is a large coronal hole responsible for a solar wind stream
heading our way. It could result in some active geomagnetic
conditions this weekend, but so far only unsettled conditions are
predicted through Sunday, with a planetary A index around 15.

Note that the vernal equinox is coming up this week, a wonderful
time for HF propagation. On the first day of spring the night and
day will be exactly 12 hours each, all over the world, from the
equator to the poles. Over the winter in the northern hemisphere,
signals traveling to the southern hemisphere have to deal with
summertime propagation modes.

At either equinox (autumnal or vernal) the whole earth is blessed
with an even distribution of solar radiation.

For more information about propagation and an explanation of the
numbers used in this bulletin, see the Propagation page on the ARRL
Web site at, www.arrl.org/tis/info/propagation.html and
especially the article 'The Sun, the Earth, the Ionosphere,' by Carl
Luetzelschwab, K9LA.

Sunspot numbers for March 6 through 12 were 132, 191, 203, 224, 214,
142, and 109, with a mean of 173.6. 10.7 cm flux was 150.3, 149.9,
148.3, 152.7, 143.7, 141.5, and 138, with a mean of 146.3. Estimated
planetary A indices were 25, 14, 9, 11, 16, 13, and 9, with a mean
of 13.9.


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