QST de W1AW
Propagation Forecast Bulletin 20 ARLP020
From Tad Cook, K7VVV
Seattle, WA May 17, 2002
To all radio amateurs
SB PROP ARL ARLP020
ARLP020 Propagation de K7VVV
Thanks to Carl, K9LA for writing last week's bulletin. Carl writes a monthly propagation column for Worldradio, and is also the new editor of the National Contest Journal.
Solar flux and sunspot numbers declined this week. Average daily sunspot numbers were off nearly 50 points and daily solar flux was down a little over five points. Solar flux dropped quite dramatically over the past few days, from over 190 a week ago to about 183 on Sunday, 172 on Monday, 161 on Tuesday, 159 on Wednesday and 158 on Thursday. The current forecast shows flux rising to 170 early next week.
On Thursday an eruption on the sun near sunspot 9948 sent a coronal mass ejection toward earth. This was not a powerful blast, but it was earth-directed. Look for rising geomagnetic indices on Saturday and Sunday, with the possibility of aurora visible from northern latitudes.
Another coronal mass ejection raised some havoc this week. It swept past earth on May 11, sparking a geomagnetic storm and aurora, which lasted several days. Peak activity was on May 11 when the planetary A index reached 40.
Sunspot numbers for May 9 through 15 were 244, 245, 226, 210, 168, 134, and 137, with a mean of 194.9. 10.7 cm flux was 190, 191, 188, 183.3, 172, 160.7, and 159.2, with a mean of 177.7. Estimated planetary A indices were 10, 17, 40, 19, 12, 32, and 16, with a mean of 20.9.