ZCZC AP21
QST de W1AW
Propagation Forecast Bulletin 21 ARLP021
From Tad Cook, K7VVV
Seattle, WA May 21, 1999
To all radio amateurs
SB PROP ARL ARLP021
ARLP021 Propagation de K7VVV
Solar flux and sunspot numbers dropped this week, with average flux values off over 18 points and average sunspot numbers down over 33 points. May 13 and 18 were disturbed days, with planetary A indices over 20. The planetary K index reached 5 on both days, and on May 13 the high latitude K index was 7, with the high latitude A index at 46. This higher number reflects the high latitude and polar region's greater vulnerability to solar flares and proton events.
Solar flux peaked for the week at 152.2 on Sunday, and is expected to be 140 for the next few days. The planetary A index for Friday through Sunday is expected to be 8, 8 and 10. Flux is expected to reach 145 on May 27, and 150 by June 2, peaking around 170 on June 5. Look for geomagnetic disturbances due to coronal hole effects on May 26-29, with the worst conditions on the first two days of that period.
In VHF news, W7XU and N0QJM in South Dakota both worked KH7R in Hawaii on 6 meters on May 17 around 0400z.
Readers who tried last week to reach the website http://www.nwra.com/nwra/spawx/tiros.html mentioned in Propagation Bulletin ARLP020 probably were unsuccessful, because nwra.com had some problems. You are encouraged to try again this week.
Sunspot Numbers for May 13 through 19 were 118, 126, 167, 151, 148, 129 and 120 with a mean of 137. 10.7 cm flux was 147.3, 144.2, 143.6, 152.2, 145.3, 140.6 and 142.4, with a mean of 145.1, and estimated planetary A indices were 24, 9, 9, 6, 5, 23 and 10, with a mean of 12.3.
The path projection for this week is from Atlanta, Georgia.