ZCZC AP51
QST de W1AW
Propagation Forecast Bulletin 51 ARLP051
From Tad Cook, K7VVV
Seattle, WA December 17, 1999
To all radio amateurs
SB PROP ARL ARLP051
ARLP051 Propagation de K7VVV
Solar flux and sunspot numbers rose over the past week after declining for the previous few weeks. Average solar flux was up over 14 points compared to the previous week, and average sunspot numbers were up nearly 34 points. The only unstable geomagnetic day was Monday, when the planetary A index was 26. The K index was 4 or 5 for most of the day. In Alaska, the higher latitude College A index was 43, and the K index reached 6 over several three-hour periods.
On Wednesday and Thursday of this week, just before this bulletin was written, the solar flux was still rising. There are actually three solar flux readings taken every day at the Penticton, British Columbia observatory, although the noon value is the one that is reported as the official number for the day. The thrice-daily values for both days were 174.9, 178.7, 182.3, 191.6, 194, and 195. This weekend look for the flux to peak, with Friday through Sunday values around 200, 210 and 195. Geomagnetic conditions should be stable, with planetary A indices around 5, 8 and 10.
Check out a fascinating article from NASA on the web at http://science.nasa.gov/newhome/headlines/ast16dec99_1.htm concerning the lackluster numbers in the current solar cycle. While not making any prediction that we are headed for one, the article talks about the Maunder Minimum, a time long before the use of radio when there were no observed sunspots for about 70 years. This is used to illustrate the point that solar activity is highly variable.
Also see the January 2000 issue of QST for an article by ON4UN on propagation during a solar eclipse last August.
There was an interesting wire service story this week from the annual meeting of the American Geophysical Union in San Francisco concerning a solar non-event on May 10-12 when there was no detectable solar wind. The density of the wind was only two percent of normal, and without the wind to compress it, the earth's magnetic field expanded out to nearly a quarter-million miles. This event was connected to the unusual difference between the southern and northern auroral zones on May 11 mentioned in Propagation Forecast Bulletin ARLP020 from May 14.
Sunspot numbers for December 9 through 15 were 132, 130, 134, 97, 147, 139 and 148 with a mean of 132.4. 10.7 cm flux was 156.2, 164.4, 159.1, 159.2, 166.1, 168.4 and 178.7, with a mean of 164.6, and estimated planetary A indices were 12, 7, 7, 9, 26, 3 and 4, with a mean of 9.7.
Here is a path projection for this weekend from Pittsburgh, Pennsylvania.