QST de W1AW
Propagation Forecast Bulletin 40 ARLP040
From Tad Cook, K7VVV
Seattle, WA September 28, 2001
To all radio amateurs
SB PROP ARL ARLP040
ARLP040 Propagation de K7VVV
This has been an incredible week for solar activity. Your author was out of town over the weekend, and on Monday received an email from WM7D, titled "New High?". It read: "The SFI is 279."
Indeed this was a new solar flux high for this sunspot cycle, and it rose even higher two days later when it hit 282.6. The previous high solar flux was 273.5 on March 28, 2001, and before that was 262 on May 17, 2000. The high activity at the end of March and during this week would seem to shift the peak of the solar cycle forward, but that reading is always based on a smoothed running average, and is determined long after the peak.
The determination of the peak is influenced by high daily values on many days around the period of peak activity, not just on one day of high numbers. But the high activity this week is not isolated. The trends have been solidly higher for two months.
By the way, WM7D has a nice web site with lots of solar and propagation information. Find it at http://wm7d.net. Click on the Solar Resource Page, and from there find many links to various charts and images. Don't miss the "More Solar Information Links" at the bottom of that page.
Average daily solar flux rose dramatically this week from last, by nearly 45 points. Average daily sunspot numbers were up nearly 90 points!
With all the new sunspots and associated energy radiating from the sun, there were some geomagnetic upsets also. The worst days were Sunday and Wednesday, when the planetary A index was 27 and 24. Sunday had a rapid rise in geomagnetic indices, starting out the UTC day with the planetary K index at 0, then going to 5 only six hours later.
The most recent projection shows geomagnetic indices stabilizing briefly with a planetary A index of 10 on Friday, then rising to 15 on Saturday and 18 on Sunday. Projected solar flux is 265 for Friday and 260 for both Saturday and Sunday.
Since we have just passed the autumnal equinox, the fall DX season is in full effect. Now is a great time to enjoy the best propagation in years on 12 and 10 meters, which should peak over the next month or two. Of course all of this high solar activity also tends to bring geomagnetic disturbances and associated absorption, especially on high latitude paths. But when you hear the K index on WWV reported at 3 or lower, that is when conditions should be great.
Sunspot numbers for September 20 through 26 were 276, 258, 293, 275, 315, 320 and 278 with a mean of 287.9. 10.7 cm flux was 226.8, 238.6, 255.2, 258.5, 279.3, 275.1 and 282.6, with a mean of 259.4, and estimated planetary A indices were 5, 5, 10, 27, 6, 18 and 24 with a mean of 13.6.