QST de W1AW
Propagation Forecast Bulletin 27 ARLP027
From Tad Cook, K7VVV
Seattle, WA July 7, 2000
To all radio amateurs
SB PROP ARL ARLP027
ARLP027 Propagation de K7VVV
Solar flux and sunspot numbers declined again this week. Average solar flux was off nearly 14 points and average sunspot numbers were down by seven. At least the geomagnetic indices were also lower. Sometimes when solar flux is higher the increased geomagnetic activity makes things difficult for HF operators.
Last week's bulletin and the one previous, ARLP026 and ARLP025 stated that solar flux should rise after July 1. This happened as projected. ARLP026 said that solar flux should peak near 200 around July 10-13, but an updated projection shows solar flux reaching a short term maximum near 205 around July 12-13, then drifting slowly toward a minimum around 165 from July 23-26. Projections also show geomagnetic conditions as unsettled over the next month, except during a quiet period from July 12-13 when planetary A indices should be in the single digits.
As we begin the second half of 2000, it is time to review quarterly averages of solar flux indices. Average solar flux for the quarter just completed, April through June, was 182.9. The same second quarter of 1999 had an average daily solar flux of 145, and the intervening average quarterly flux values were 157,6, 175,2 and 180.5. This is a good general indication of a rising solar flux. Average solar flux for the month of June was 179.8, and the January through May average monthly levels were 159, 174.1, 208.2, 184.2 and 184.5. This seems to indicate a peak of solar flux values in March, but don't bet on March being the solar max for cycle 23. Latest predictions shown in the NOAA weekly Preliminary Report and Forecast predict a peak of smoothed solar flux values at 188 for August and September, 2000 and smoothed sunspot numbers reaching a maximum of 140 in January and February, 2001. Smoothed numbers are averaged over a period of time, so we can expect peak values somewhat higher. You can see the predicted values in a pdf file at http://www.sec.noaa.gov/weekly/pdf/prf1296.pdf. Page through to the last few pages to see the tables and graphs. The URL for the index to all of the weekly reports is at http://www.sec.noaa.gov/weekly/index.html.
Expect fairly good conditions for the IARU HF World Championship this weekend. Predicted solar flux values for Friday through Tuesday are 180, 185, 190, 195 and 200, and predicted planetary A indices for the same days are 15, 10, 12, 10 and 10.
Sunspot numbers for June 29 through July 5 were 189, 159, 175, 185, 166, 165 and 200 with a mean of 177. 10.7 cm flux was 163.3, 159.6, 163.7, 162.4, 156.3, 158.4 and 168.7, with a mean of 161.8, and estimated planetary A indices were 12, 7, 9, 6, 10, 9 and 13, with a mean of 9.4.