ZCZC AP35
QST de W1AW
Propagation Forecast Bulletin 35 ARLP035
From Tad Cook, K7VVV
Seattle, WA August 28, 1998
To all radio amateurs
SB PROP ARL ARLP035
ARLP035 Propagation de K7VVV
Feel the solar wind? This has been a very active week for the geomagnetic field, with solar flares and resulting geomagnetic storms creating lots of excitement. On the day that this was written the planetary A index, which recently has normally been below 10, was at 112, and 39 the day before. Currently a major geomagnetic storm is raging, but conditions are expected to settle down this weekend.
Solar flux was down slightly from last week and the week before, while the average solar flux for the previous ninety days rose from 115 to 117. Solar flux was above these values on every day this week, indicating a general upward trend. A year ago the average solar flux for the week was 78.9, almost fifty points lower than the current level. Average sunspot numbers were about 100 points lower.
On August 24 there was a major proton flare. This caused a major shortwave fadeout, plus continuing geomagnetic disturbances. The flare was big enough to merit reporting in the news wire services. Reuters reported that the aurora may be strong enough to be visible across the United States, not just in the northern latitudes.
Conditions such as this are very bad for HF propagation, but create many interesting VHF contacts via the aurora. K2SMN in New Jersey reported working VE2BKL and VE2PEP in Quebec, WA4HEI in Michigan, and W9JN in Wisconsin, all on two meters.
Look for conditions to calm down this weekend. Solar flux for Friday through Sunday is forecast at 135 for all days, and the planetary A index is predicted to be 30, 15 and 10 over the same period. Solar flux is expected to drop down near 115 for September 1 and 2, then peak around 145 around a week later. There is a strong possibility of recurrent coronal holes causing geomagnetic disturbances around September 18 and 19.
The author can be contacted via email at tadssc.com, or via packet at K7VVV N7FSP.WA.USA.NOAM.
Sunspot Numbers for August 20 through 26 were 120, 138, 102, 121, 99, 109 and 146 with a mean of 119.3. 10.7 cm flux was 138.6, 132.1, 132.9, 126.4, 121.2, 122.1 and 126.9, with a mean of 128.6, and estimated planetary A indices were 18, 6, 23, 23, 11, 11, and 39, with a mean of 18.7.