QST de W1AW
Propagation Forecast Bulletin 51 ARLP051
From Tad Cook, K7VVV
Seattle, WA December 6, 2002
To all radio amateurs
SB PROP ARL ARLP051
ARLP051 Propagation de K7VVV
Average sunspot numbers were up a bit this week, and average daily solar flux barely changed. Geomagnetic indices were quieter.
Now that December is here, let's review average daily solar flux and sunspot numbers for November, and compare them with previous months. Here are monthly averages for solar flux and sunspot numbers for this year. From January through November, 2002 the average daily sunspot number for each month was 189, 194.5, 154.3, 144.4, 146, 183.5, 191, 206.4, 153.9 and 159.8. Average daily solar flux for the same months was 227.3, 205, 179.2, 141.4, 148.7, 174.4, 183.9, 175.8, 167 and 168.7.
This weekend is the ARRL 160-Meter Contest. It would be good to have low geomagnetic activity for this contest. Right now the predicted planetary A index for Friday through Monday is 12, 15, 20 and 15. This indicates unsettled to active conditions on Saturday and Sunday due to coronal hole effects. There is a chance of moderate solar flare activity over the next few days. Solar activity is likely to be low. Predicted solar flux for the next few days is 160-175.
Chester, KD5TFK wrote in to ask, "How much longer can we expect great propagation on 10-meters?" He assumes we are on the downside of the current solar cycle.
One way to look at this is to compare likely conditions for the 10-meter contest coming up the weekend of December 14-15. Last year the average daily solar flux around the time of the contest was about 228. This year it is likely to be about 175. If we check the weekly Preliminary Report and Forecast of Solar Geophysical Data from the NOAA SEC web site at http://www.sec.noaa.gov/weekly/index.html, they run an occasional prediction for smoothed sunspot and solar flux numbers. The last prediction was at the end of the November 5 issue. The smoothed flux value they are predicting for December 2003 is about 41 points lower than for December 2002, so let us use a value of 134 for December of next year. Next try plugging these dates and values into W6ELprop (see the site, http://www.qsl.net/w6elprop/ ).
If I do a 10-meter prediction for last December from Seattle to Japan using a flux value of 228, I show a good predicted opening from 2230-0130z with a relative dB level of 21. Run the same test with a solar flux of 175, and the period shortens to 2230-0030z. Do it again with 134 for the solar flux, and it shows a possibility of an opening around 2300z.
Try it again on 10-meters from Dallas to Brazil. Last year has a strong opening from 1300-0030z, this year 1330-2330z, and next year 1400-2200z. The solar activity will gradually decrease, and 10-meters will be affected.
Sunspot numbers for November 28 through December 4 were 124, 107, 150, 97, 155, 135, and 144, with a mean of 130.3. 10.7 cm flux was 139.7, 141.3, 146.2, 149.6, 146.1, 145.9, and 148.7, with a mean of 145.4. Estimated planetary A indices were 15, 14, 16, 16, 11, 11, and 12, with a mean of 13.6.