ZCZC AP51
QST de W1AW
Propagation Forecast Bulletin 51 ARLP051
From Tad Cook, K7VVV
Seattle, WA December 19, 1997
To all radio amateurs
SB PROP ARL ARLP051
ARLP051 Propagation de K7VVV
Solar activity was down last week. Not only was the solar flux below the average for the previous 90 days on six out of seven days, but the 90 day average actually dropped one point. Average solar flux last week dropped nearly 12 points when compared to the previous week. Solar flux was also lower than expected for the 10 meter contest last week.
Solar flux is expected to stay below 90 until December 22, then rise above 100 around December 27, and drop below 100 again around January 1. A recurring coronal hole is expected to increase geomagnetic instability resulting in higher K and A indices around December 21 and 22.
Sunspot Numbers for December 11 through 17 were 99, 64, 70, 66, 56, 43 and 42 with a mean of 62.9. 10.7 cm flux was 96..4, 92.5, 89.3, 90, 89.1, 84.7 and 85.6, with a mean of 89.7, and estimated Planetary A indices were 13, 2, 2, 2, 3, 3, and 3, with a mean of 4.