QST de W1AW
Propagation Forecast Bulletin 42 ARLP042
From Tad Cook, K7VVV
Seattle, WA October 17, 1997
To all radio amateurs
SB PROP ARL ARLP042
ARLP042 Propagation de K7VVV
Judging from the high solar flux and sunspot activity over a month ago, recently we expected to see more of that same activity, since the Sun rotates relative to Earth once every 27.5 days. Unfortunately by the time the rotation was complete, most of those active regions were gone.
This week we saw solar activity up only by a little. On five out of seven days the solar flux was above the average for the previous ninety days. Geomagnetic activity was up a lot though over last weekend, when the Estimated Planetary K Index was up to six over several periods. This is a very high value, indicating very stormy conditions with high absorption of radio signals.
The most recent forecast indicates a small rise in solar flux into the low nineties next week, peaking around October 22 and 23, then dropping back to the mid-eighties before the end of the month. In November look for unsettled to active geomagnetic conditions around the 5th and 6th.
The NOAA Space Environment Center reported that a panel of solar experts met recently and fixed the probable date for the recent solar minimum around October, 1996, with a possible range from May through December. Panelists believe that Cycle 23 should be a large cycle, but not as big as Cycle 19 in the late nineteen fifties. They expect it to peak around March, 2000, with a range from June, 1999 to January, 2001. This places the peak in the very near future, but sunspot cycles go up much faster than they go down.
Sunspot Numbers for October 9 through 15 were 27, 44, 31, 60, 44, 44 and 47 with a mean of 42.4. 10.7 cm flux was 83.5, 84.2, 86.1, 88.7, 88.3, 84.8 and 86.9, with a mean of 86.1, and estimated planetary A indices were 19, 27, 26, 7, 7, 5, and 4, with a mean of 13.6.