ZCZC AP39
QST de W1AW
Propagation Forecast Bulletin 39 ARLP039
From Tad Cook, K7VVV
Seattle, WA September 26, 1997
To all radio amateurs
SB PROP ARL ARLP039
ARLP039 Propagation de K7VVV
Solar activity was down, but still quite good this past week after the recent big rise in solar flux. The running average of solar flux for the previous 90 days rose another two points this week to 81, and the flux on every day was still above the moving average, now for the 51st day.
Solar flux dipped down only to 85.2, but is now climbing back up. Look for the increase to continue, reaching the mid nineties by October 2, and over 100 again between October 7 to 11. Flux values are expected to dip below 90 after mid month, and back above 90 a few days later. Of course this is based on the previous solar rotation, and new active areas could emerge which would drive the numbers higher.
The Sun has spewed forth several coronal mass ejections recently, so expect the resulting high speed solar wind to cause unstable geomagnetic conditions around September 28 to 30. This may cause some problems for the RTTY contest this weekend.
The worst day this past week in terms of geomagnetic instability was September 18, when the planetary K index was up to 4 and 5 over several 3 hour periods.
With the rising solar flux and the Fall season comes better propagation on 10 and 15 meters, so we are no longer as dependent on 20 meters for long distance communication.
Sunspot Numbers for September 18 through 24 were 30, 18, 15, 39, 47, 48 and 47 with a mean of 34.9. 10.7 cm flux was 88.1, 89.2, 87.7, 85.2, 88.9, 91.7 and 92.9, with a mean of 89.1, and estimated planetary A indices were 17, 3, 7, 15, 8, 4, and 4, with a mean of 8.3.