QST de W1AW
Propagation Forecast Bulletin 51 ARLP051
From Tad Cook, K7VVV
Seattle, WA December 22, 2000
To all radio amateurs
SB PROP ARL ARLP051
ARLP051 Propagation de K7VVV
Average solar flux and sunspot numbers were up sharply this week. The solar flux average for the week was up over 47 points and sunspot numbers rose over 85 points. It has been a quiet week geomagnetically, with planetary A indices in the single digits.
Solar flux probably peaked at 2200z on December 20, when it reached 207.7. Solar flux is predicted over the next few days, Friday through Monday at 195, 195, 190 and 190. The planetary A index for those days is predicted at 12, 15, 15 and 12. The reason for the unsettled geomagnetic condition is a coronal mass ejection on December 18 that is expected to cause a weak disturbance.
Beyond this weekend look for solar flux to drop to a short term minimum of 140 around January 3-5. The next peak is expected from January 16-19.
Check the bottom of Jan Alvestad's Solar Terrestrial Activity Report at http://www.dxlc.com/solar/. He has a table showing monthly averages of solar flux and sunspot numbers, as well as a smoothed sunspot number. According to his table, the highest average monthly solar flux was in March of this year, although July was almost as high. The highest sunspot number was in July, and during April he shows a smoothed sunspot number of 120.8, which may be the peak of this solar cycle. The peak of cycle 23 has probably passed, although we could get an increase in activity which would extend the peak. Fortunately, sunspot cycles seem to go up faster than they decline.
Sunspot numbers for December 14 through 20 were 157, 181, 217, 229, 174, 163 and 183 with a mean of 186.3. 10.7 cm flux was 182.2, 187.8, 190.5, 196.7, 198, 198.6 and 201.3, with a mean of 193.6, and estimated planetary A indices were 4, 3, 4, 8, 10, 5 and 4 with a mean of 6.3.