ZCZC AP40
QST de W1AW
Propagation Forecast Bulletin 40 ARLP040
From Tad Cook, K7VVV
Seattle, WA October 2, 1998
To all radio amateurs
SB PROP ARL ARLP040
ARLP040 Propagation de K7VVV
Solar activity was down a bit last week, with the average solar flux off by six points and average sunspot numbers lower by almost 27 points.
Now that September is over it's time to look at some long term trends. The last quarter of 1997 had an average solar flux of 94.3. The next quarter, January through March of 1998, the average flux rose to 98.8. The second quarter of this year the average flux was 107.8, and this last quarter the average flux was 129.2.
The average flux for September was 137.7, and for May through August it was 106.7, 108.5, 114.1 and 136. The average flux over this past week was 125.6, and for the same period one year ago it was only 88.2. We can see that the general trend in solar activity is up, although there was only a negligible increase from August to September.
Last week the really active geomagnetic day was on Friday, when the planetary A index was 121 and the planetary K index went as high as 9, which signals a major geomagnetic storm.
Over the next few days, Friday through Sunday, the solar flux is forecast to be 115, 113 and 112, and the planetary A index for the same period is predicted at 20, 20 and 15. Unsettled to active conditions are predicted around October 15 and for October 18-23 as well. The solar flux is expected to rise after the weekend, to above 130, then drop down to 120 around October 12-14, then peak around 145 around October 20. Now that we are in the fall season, look for good HF propagation when the K and A index is low.
If you have access to the web, check NASA Space Science News at www.astronomynews.com and look for the September 29 article under Astrophysics titled Crusty Young Star Makes its Presence Felt. This is about the big gamma ray flash which blasted the earth on August 27, which was widely reported this past week in the news media.
On that day the planetary A index was 112, and it was assumed at the time that this was caused by a proton flare from our sun about 4 days earlier. Now some scientists are wondering if perhaps the resulting disturbance on earth may have been enhanced by a wave of energy from a Magnetar, or super-magnetized star about 15,000 light years from earth. Paul Harden, NA5N of the National Radio Astronomy Observatory in New Mexico wants to hear from hams who may have been listening to medium wave or HF radio around 3:22 AM Pacific Daylight Time (1022 UTC) in the Western United States on August 27. He can be reached at pharden@nrao.edu.
Paul says that this is the first known event from outside our solar system that has affected the earth's environment. He also invites us to look at his institution's web page on this event at www.nrao.edu/pr/magnetar.html. He noted that if only the SOHO satellite had been working, meaningful measurements could have been made which could easily separate the effects of the solar flare and the magnetar gamma ray burst.
The October 1998 issue of the magazine Astronomy has a couple of items of interest to solar observers. Page 28 has a stunning picture from the NASA Transition Region and Coronal Explorer spacecraft showing loops of plasma from an active solar region on April 25. The same issue on page 60 has an article about forecasting solar storms titled Blowin' in the Solar Wind.
Sunspot Numbers for September 24 through 30 were 156, 118, 115, 87, 127, 86 and 59 with a mean of 106.9. 10.7 cm flux was 135.4, 122.1, 126.9, 135, 122.5, 115.9 and 121.5, with a mean of 125.6, and estimated planetary A indices were 28, 121, 14, 12, 6, 10, and 8, with a mean of 28.4.