QST de W1AW
Propagation Forecast Bulletin 21 ARLP021
From Tad Cook, K7VVV
Seattle, WA May 24 2002
To all radio amateurs
SB PROP ARL ARLP021
ARLP021 Propagation de K7VVV
Sunspot counts and solar flux reached a short-term minimum late last week, but both seem to be on the rise again. Average daily sunspot numbers were down nearly 35 points from last week. Average solar flux was down eight points. Predicted solar flux for this weekend is 175 for Friday and 170 for both Saturday and Sunday. Flux values are expected to rise to around 190 by month's end.
Geomagnetic disturbances are the bigger news this week, with a geomagnetic storm on Thursday, May 23, caused by a series of three coronal mass ejections the previous day. The Planetary A index was 54 on Thursday, and the planetary K index reached seven over two three-hour periods. This means generally lousy HF radio conditions with enhanced absorption, especially at higher latitudes.
Several sunspot groups in view offer the potential for more fireworks. Currently the predicted A index for Friday through Sunday is 30, 15 and 10. The high A and K values don't look good if they persist during this weekend's CQ Worldwide WPX CW Contest, but if there are no more coronal mass ejections or flares, the bands could recover. As this was being written on Thursday evening the planetary K index had dropped to three. So had the mid-latitude K index, as reported by WWV.
NW7US sent along a tip for propagation watchers who have WAP-enabled wireless devices. Point your WAP device to the NW7US Amateur and Shortwave Radio Command Center. A normal Web browser will get redirected but a cell phone will see WML instead of HTML providing solar and geomagnetic information.
KB6HCN recently sent along a URL to a nice image of the sun. See Astronomy Picture of the Day. For a larger image click on the photo.
Sunspot numbers for May 16 through 22 were 120, 134, 140, 155, 171, 185, and 217, with a mean of 160.3. The 10.7-cm flux was 158.4, 157.1, 163, 170.9, 171.3, 185.9, and 181.1, with a mean of 169.7. Estimated planetary A indices were 12, 10, 15, 18, 14, 14, and 14, with a mean of 13.9.