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ARRL Propagation Bulletin ARLP008 (2003)

ARLP008 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 8  ARLP008
From Tad Cook, K7VVV
Seattle, WA  February 21, 2003
To all radio amateurs 

ARLP008 Propagation de K7VVV

Sunspot numbers were lower this week, into the double-digits below
100. The average daily number was about 54% lower than the previous
week, and daily average solar flux was off by nearly 20 points, or
about 14%.

Earth has been affected by a high-speed solar wind since February
15, and this hurt conditions during the ARRL CW DX contest last
weekend, at least in the higher latitudes. Both mid-latitude and
planetary K indices were as high as 4 on Saturday and Sunday, and
Alaska's high-latitude College K index was up to 6 on both days.

This was especially detrimental to signals traveling over polar
paths. But in a few days conditions had improved, and on Wednesday
evening during a visit to K7SS, I had good signal reports into
Kuwait running 100 watts beaming over the pole using his new
3-element continuously tunable stepper Yagi.

Geomagnetic conditions are expected to be unsettled on Friday, with
a planetary A index around 20. Solar flux should rise, with
predicted values of 120 for Friday and Saturday and 125 for Sunday
and Monday. Current projections show solar flux peaking around 150
from March 6-8.

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, and,
especially, the article "The Sun, the Earth, the Ionosphere," by
Carl Luetzelschwab, K9LA.

Sunspot numbers for February 13 through 19 were 113, 113, 96, 41,
16, 51, and 57, with a mean of 69.6. 10.7 cm flux was 130.6, 131.4,
123.6, 118.5, 112.1, 109.9, and 116.3, with a mean of 120.3.
Estimated planetary A indices were 8, 19, 18, 15, 11, 17, and 12,
with a mean of 14.3.


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