QST de W1AW
Propagation Forecast Bulletin 36 ARLP036
From Tad Cook, K7VVV
Seattle, WA September 5, 1997
To all radio amateurs
SB PROP ARL ARLP036
ARLP036 Propagation de K7VVV
Solar activity continues another week of good conditions with heightened sunspot numbers and solar flux. There are a number of good indicators, and one is that the average solar flux for the previous ninety days rose two points this week to 75, while the solar flux on every day this week was high above this average. Solar flux above the moving average indicates a positive trend, and this has been the case for a month now. The last day that the solar flux was below the ninety day average was back on August 4, so this is a good indication that cycle 23 may finally be under way.
Along with the increased solar activity came geomagnetic instability caused by coronal mass ejections. The planetary A index has been 19 for the past two days, and was also in the teens at the end of August. Look for possible instability again around September 24 and 25.
Based on the previous solar rotation, solar flux may dip below 80 after September 10, then above 80 ten days later, and above 90 after September 25. Over Friday, Saturday and Sunday this week it is expected to be around 93, 90 and then 85.
An August 28 news article on the Reuters wire service detailed some findings from the Michelson Doppler Imager--which is aboard the Solar and Heliospheric Observatory--watching the Sun from almost one million miles from Earth. The article mentioned complex patterns of currents below the Sun's surface which produce sunspots when they contact plasma. These streams can rub against each other and the opposing forces shoot out material in the form of solar flares.
In other news NASA launched the new Advanced Composition Explorer solar observatory, which is on a five year mission to study solar flares and provide earlier warning of solar storms. It will monitor particles streaming from the Sun, and scientists hope to be able to predict geomagnetic storms an hour earlier than at present.
Sunspot Numbers for August 28 through September 3 were 61, 67, 69, 80, 90, 67 and 55 with a mean of 69.9. 10.7 cm flux was 90.5, 91.5, 92, 96.4, 93.4, 91.7 and 93.1, with a mean of 92.7, and estimated planetary A indices were 16, 15, 11, 4, 4, 5, and 19, with a mean of 10.6.