ZCZC AP01
QST de W1AW
Propagation Forecast Bulletin 1 ARLP001
From Tad Cook, K7VVV
Seattle, WA January 2, 1998
To all radio amateurs
SB PROP ARL ARLP001
ARLP001 Propagation de K7VVV
Conditions were good for the last week of 1997 with higher solar activity than the previous week and mostly low geomagnetic activity. The exception was on December 30, when the global K index went as high as six and the global A index was 25. This was due to a coronal mass ejection on December 26 as well as a coronal hole. On the last day of the year the average solar flux for the previous 90 days rose from 94 to 95, and the solar flux was above that level each day of the week.
Average solar flux has steadily risen over this past year, particularly in the second half. Average solar flux for the first quarter of 1997 was 73.8, and 73.6 for the second, 82 for the third and 94.3 for the fourth quarter. Look for steadily rising figures in 1998. (The reason that 94.3 for the last quarter is not the same as the 95 average for the previous 90 days is that the last quarter was all of October through December, which was actually 92 days. The 95 number mentioned in the previous paragraph is rounded up, and the difference in averages is only .18.)
For the short term, we should have fair conditions for the ARRL RTTY Roundup this weekend. There are no predicted geomagnetic disturbances, and the solar flux for January 2-4 is forecast at 98, 93 and 90. The latest projection shows the solar flux going down to the mid to high eighties, then back above 90 around January 16, and above 100 after January 21.
Sunspot Numbers for December 25 through 31 were 56, 50, 56, 55, 79, 56 and 64 with a mean of 59.4. 10.7 cm flux was 104.7, 104.7, 95.9, 102.1, 104.4, 101.3 and 104.5, with a mean of 102.5, and estimated planetary A indices were 2, 1, 2, 2, 3, 25, and 4, with a mean of 5.6.