ZCZC AP10
QST de W1AW
Propagation Forecast Bulletin 10 ARLP010
From Tad Cook, K7VVV
Seattle, WA March 6, 1998
To all radio amateurs
SB PROP ARL ARLP010
ARLP010 Propagation de K7VVV
Average sunspot numbers were slightly higher and average solar flux was only a little lower last week. The average solar flux for the previous 90 days declined one point to 95, and flux values were above that level for three days out of the week.
KC7ZMV wrote with an interesting observation about the comparison of the previous two solar cycles with the current cycle on the web at http://www.dxlc.com/solar/cyclcomp.html, as mentioned in the last propagation bulletin, ARLP009. Jim noted that the website claims that the current cycle began in May 1996, but he has read elsewhere that October 1996 is a better date. If one accepts the later date, then perhaps the current cycle isn't really lagging the other cycles.
NOAA has the announcement about the revised date at http://sec.noaa.gov/info/SumSept.html. Looking at the charts at the cycle comparison site, it isn't clear whether the graphs are really drawn from the beginning of each cycle or from the minimum. Since they are moving averages, the trend line lags behind the current data about six months.
If one looks out beyond the trend line on the current cycle it appears that the data has leveled out, and this is born out in the current monthly average just calculated. The monthly average solar flux values for November through January were 99.5, 98.7 and 93.4, and in February the average flux was 93.4, precisely what it was in January. We can hope for better, but it still looks like solar activity is lagging.
Conditions should be fairly good for the ARRL International DX SSB Contest this weekend, with predicted solar flux for Friday through Sunday at 94, 92 and 90. No geomagnetic disturbances are foreseen. Solar flux should increase after the weekend, rising above 100 around March 13 and dipping back into the high nineties after March 17.
Sunspot Numbers for February 26 through March 4 were 69, 78, 60, 93, 105, 56 and 55 with a mean of 73.7. 10.7 cm flux was 92.7, 90.3, 94, 98.3, 91.5, 96.6 and 101.7, with a mean of 95, and estimated planetary A indices were 3, 4, 12, 12, 14, 4, and 8, with a mean of 8.1.