QST de W1AW
Propagation Forecast Bulletin 3 ARLP003
From Tad Cook, K7VVV
Seattle, WA January 19, 2001
To all radio amateurs
SB PROP ARL ARLP003
ARLP003 Propagation de K7VVV
Average solar flux dropped a little more than two points, and average sunspot numbers declined 22 points over the past week. On Wednesday the sunspot number dropped below 100 for the first time since December 12. The outlook for the near term is for continued low activity.
Last week's update mentioned a predicted short-term solar flux peak around 200 on January 17, but instead it was only 151.9. The largest sunspot group is rotating out of view around the sun's western limb, and the near-term outlook is for solar flux to continue declining for the next few days to a minimum of 140 on January 21. It then should rise to 170 on January 25, and stay around 175 from January 26 through February 1, peaking at 180 on February 2 or 3.
These numbers are far below recent values of more than 200 and are another sign that we have passed the peak of the solar cycle. But along with this decline in activity come stable geomagnetic conditions, as the chance for solar flares declines along with the sunspot activity. Planetary A indices are expected to remain in the single digits until the end of this month. With the longer winter nights, this looks good for DX on 160, 80 and 40 meters.
Not only are we experiencing stable geomagnetic conditions, but in the northern hemisphere, atmospheric noise is also at a seasonal low. The higher bands (20 meters and above) remain good during the day, but because of the season 20 meters is not open late into the evening as it was in the fall. Of course, the southern hemisphere is experiencing summer right now.
On January 20, Earth is expected to move through a solar wind coming from a small coronal hole, but no geomagnetic disturbance currently is predicted.
Sunspot numbers for January 11 through 17 were 173, 173, 146, 181, 154, 115 and 71 with a mean of 144.7. The 10.7-cm flux was 165.9, 178.3, 184.3, 176.3, 169.2, 161.9 and 151.9, with a mean of 169.7. The estimated planetary A indices were 5, 7, 5, 8, 7, 6 and 7 with a mean of 6.4.