ZCZC AP08
QST de W1AW
Propagation Forecast Bulletin 8 ARLP008
From Tad Cook, K7VVV
Seattle, WA February 21, 2003
To all radio amateurs
SB PROP ARL ARLP008
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, http://www.arrl.org/tis/info/propagation.html 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.