January 4, 1999

ZCZC AP01

QST de W1AW

Propagation Forecast Bulletin 1 ARLP001

From Tad Cook, K7VVV

Seattle, WA January 4, 1999

To all radio amateurs

SB PROP ARL ARLP001

ARLP001 Propagation de K7VVV

WA4TTK has a new data file for his Solar Data Plotting Utility available at http://edge.net/~scraig/sol.htm. This has all the sunspot and solar flux data for the last ten years, through December 31, 1998. You can download Scott's freeware, or just update your data if you have fallen behind. The latest version of his plotting utility automatically sucks up the numbers from this weekly bulletin so it is easy to keep your data fresh.

With an updated data file covering a decade of solar observations, the beginning of the new year is a good time to look at some of the numbers and crunch them for some trends.

The average annual solar flux for 1990 through 1997 was 188, 205.2, 150.4, 109.5, 85.8, 77.1, 70.8, and 81, and for 1998 it was 117.9. We can see that the peak year for the last cycle was probably 1991 and the year of the quiet sun was 1996. The rise for 1998 indicates a good upward trend.

Here are some quarterly numbers for this year. The last quarter of 1997 had an average solar flux of 94.3. The average flux values for the four quarters of 1998 were 98.8, 107.8, 129.2, and 135.4. Monthly solar flux averages for May through December, 1998 were 106.7, 108.5, 114.1, 136, 137.7, 117.3, 138.8 and 150.1.

And what about last week? Solar activity was way up, with solar flux peaking at 184.4 on December 22. Solar flux values have not been this high in nearly six years, since February 9, 1993, in the last solar cycle. This was much higher than forecast in last week's bulletin, and exciting news for HF operators.

For this weekend, the solar flux for Saturday through Monday is forecast to be fairly high at 165 for all three days, and a moderate planetary A index of 8 for those days as well. This indicates fairly stable geomagnetic conditions. Over the past week the most active days were December 26 and 29, when the planetary A index was 16. The quietest days were December 27 and 31, when the planetary A index was three and K indices were down to zero.

Over the next week look for the solar flux to stay above 150, dropping below that level around January 12. Solar flux should rise above 160 by January 18, and back to 180 around January 25. No big geomagnetic disruptions are predicted, but of course this is based only on what is known from the last solar rotation.

Have fun and good DX in 1999.

Sunspot Numbers for December 24 through 30 were 93, 84, 100, 156, 177, 136 and 186 with a mean of 133.1. 10.7 cm flux was 139.4, 144.4, 144.9, 166.8, 184.4, 182.8 and 179, with a mean of 163.1, and estimated planetary A indices were 3, 11, 16, 3, 5, 16 and 6, with a mean of 8.6.