QST de W1AW
Propagation Forecast Bulletin 1 ARLP001
From Tad Cook, K7VVV
Seattle, WA January 5, 2001
To all radio amateurs
SB PROP ARL ARLP001
ARLP001 Propagation de K7VVV
On January 2 and 3 a large sunspot group, number 9289, crossed the center of the visible solar disk. This is the area that has the greatest effect on the earth. It covered 890 millionths of the solar disk, which is an area five times the surface of the earth. On January 4 around 0900z the earth reached perihelion, which is the closest it will be to the sun all year. Sunlight at perihelion is about 7 percent more intense over the whole of the earth than it is in July.
KD5MSW sent reminders of a couple of sites for viewing the sun. One is a live real time image of the sun at http://www.sunspot.noao.edu/LIVE/index.html. The other, at http://sohowww.nascom.nasa.gov/data/realtime/mpeg/ gives movies of the sun taken from satellites.
Sunspot numbers and solar flux were down over the past week, with the weekly average sunspot number off over 20 points and the average solar flux declining nearly 14. Geomagnetic conditions were very quiet, with Wednesday having only moderately unsettled conditions, with a planetary A index of 11. The high-latitude College A Index in Fairbanks, Alaska was 22 on that day, but the day before it was actually 0. This is unusually low, especially for such a high latitude location where any solar event aimed toward earth seems to cause upset and absorption for polar HF signals. The College K index was also 0 for each 3-hour period, except for the last period of the UTC day, when it was 1.
Solar flux is expected to continue to fall over the next few days, and reach a short term minimum around January 9 or 10. The next solar flux peak is expected around January 18-21. Unsettled geomagnetic conditions are expected with a planetary A index of 15 for January 5 and 6, stabilizing slightly to an A of 12 for January 7 and 8.
Now as promised in last week's bulletin, it is time to review the numbers for last year, and perhaps divine when the peak of this sunspot cycle occurred.
The yearly averages of daily sunspot numbers for 1995-2000 were 28.7, 13.2, 30.7, 88.7, 136.3 and 174.4. The yearly averages of daily solar flux numbers for 1995-2000 were 77.1, 73.4, 81, 117.9, 153.7 and 181.2. We can see that the minimum activity was centered around 1996 and that the maximum was in 2000.
If you use WA4TTK's solar plotting software with the data from these bulletins, you can see from the chart that there were a couple of high points in activity this year. The first was May 17 when the solar flux was 262 and sunspot number 342. The second was July 18-20, when sunspot numbers were 343, 342 and 401 and solar flux was 261.9, 249.9 and 252.9. Examination of the graph shows a general drop in activity since July. (If you don't have the solar plotting software, you can get it for free from WA4TTK's web site at http://edge.net/~scraig/index.html or specifically http://www.craigcentral.com/sol.htm. Note that you can also download an updated data file, which has all of the solar flux and sunspot data from this bulletin from January 1, 1989 through December 31, 2000.)
These peaks suggest a solar maximum around May or July. Since there is so much daily variation in the data (even at the cycle peak), it is useful to look at averages. The monthly averages of daily sunspot numbers for 2000, January through December, were 140.8, 161.9, 203.6, 193.4, 188.8, 190.3, 236.7, 166.7, 169.9, 138.9, 149.9 and 146.4. The 236.7 number for July was the highest for the year. Monthly Average of daily solar flux for the year was 159, 174.1, 208.2, 184.2, 184.5, 179.8, 200.5, 163.1, 201.7, 167.7, 178.8 and 173.6. This gives us three peaks, in March, July and September. The quarterly daily sunspot averages were 168.9, 190.8, 193.1 and 145, and quarterly solar flux was 180.5, 182.9, 188.3 and 173.3. These suggest a maximum in the third quarter, July through September.
Ultimately the solar physicists who represent the real scientific expertise will come up with an approximate date for the peak using a smoothed moving average, but the data is not all here yet.
Contests this weekend include the ARRL RTTY Roundup and the Low Band CW portion of the Japan International DX Contest. Since this involves working Japanese stations only and only on 160, 80 and 40 meters, below are some path projections to Japan. We have not attempted 160 meter path projections in the past, but here is an attempt. 160 meter operators may email observations to the author at email@example.com.
Sunspot numbers for December 28 through January 3 were 159, 150, 140, 153, 119, 143 and 128 with a mean of 141.7. 10.7 cm flux was 185.4, 181.5, 182.1, 169.5, 171, 176.1 and 169.9, with a mean of 176.5, and estimated planetary A indices were 5, 6, 2, 2, 3, 4 and 11 with a mean of 4.7.