QST de W1AW
Propagation Forecast Bulletin 7 ARLP007
From Tad Cook, K7VVV
Seattle, WA February 18, 2000
To all radio amateurs
SB PROP ARL ARLP007
ARLP007 Propagation de K7VVV
Solar flux and sunspot counts increased the week before last, fell last week, and the averages for both weeks were about the same. Average solar flux was down about 11 points last week, and average sunspot numbers were off by a little over one point. Last weekend had a surprising burst of geomagnetic activity, when Saturday's planetary A index was 52. The planetary K index was as high as 7, and Alaska's College A index, which is frequently higher because of its proximity to the pole, was 71. During a six hour period, from 0600-1200z, the planetary A index was 7 and 6 while the College A index was 8 and 7. These all indicate severe geomagnetic storm levels.
What should we see over the next week? For the next five days, Friday through Tuesday, solar flux is predicted to be 155, 150, 150, 145 and 145. Planetary A index for those same days is forecast to be 5, 5, 12, 8 and 8. For best HF conditions, we want a low A index in the single digits, and rising solar flux. So Sunday, February 20 with a planetary A index of 12 could be somewhat unsettled.
Solar flux for the short term is expected to bottom out near 130 around February 25, then rise to about 150 by March 1, but peak broadly and fairly low near 175 around March 4-8. The next predicted short term minimum is forecast for March 23-24. Of course these are all guesses based upon activity over previous solar rotations, which occur about every 27.5 days. Since the predicted high levels of 175 are much lower than previous rotations where solar flux was above 200, this means that the prediction is based upon sunspot regions which are currently fading. Any new sunspot areas will probably result in increased solar flux and better HF conditions. With spring coming, it would be nice to see extended worldwide openings on 10 and 12 meters again, which would accompany the high flux levels normally expected in a peak year of a solar cycle.
Sunspot numbers for February 10 through 16 were 172, 184, 157, 147, 158, 158 and 182 with a mean of 165.4. 10.7 cm flux was 175.7 170.2, 163.2, 159.9, 158.7, 156 and 160.2, with a mean of 163.4, and estimated planetary A indices were 7, 13, 52, 14, 29, 11 and 5, with a mean of 18.7.
Path projections for this weekend are from a place in Arizona between Tucson and Phoenix, near Eloy.