ZCZC AP53
QST de W1AW
Propagation Forecast Bulletin 53 ARLP053
From Tad Cook, K7VVV
Seattle, WA December 20, 2002
To all radio amateurs
SB PROP ARL ARLP053
ARLP053 Propagation de K7VVV
Again this week geomagnetic indices were lower than the previous week. During November 28 through December 4 the average planetary A index was 13.6, the next week it was 9.7, and this week it was 7.7. This was good for HF conditions, along with a rising solar flux. Average solar flux for the same three weeks was 145.4, 153.2 and 188.7, and average daily sunspot numbers were 130.3, 146.1 and 206.1.
Quiet conditions came to an end on December 19 when the planetary A index jumped to 21. This is due to a solar wind stream flowing from a coronal hole. Geomagnetic activity is expected to decline, and in a few days solar flux values should slip below 190.
Winter solstice comes this weekend, so the long nights will soon turn gradually shorter. Currently the darkness favors the lower HF bands, but as the day lengthens in the Northern Hemisphere higher frequency propagation will improve.
Sunspot numbers for December 12 through 18 were 129, 176, 214, 217, 194, 252, and 261, with a mean of 206.1. 10.7 cm flux was 153.1, 166.9, 185.9, 203, 202.9, 212.5, and 196.9, with a mean of 188.7. Estimated planetary A indices were 7, 7, 11, 9, 8, 6, and 6, with a mean of 7.7.