ARLP019 Propagation de K7RA:
May 9, 2003

Propagation Forecast Bulletin 19 ARLP019
From Tad Cook, K7RA
Seattle, WA May 9, 2003
To all radio amateurs

ARLP019 Propagation de K7RA

Active geomagnetic conditions continue and seem to stretch into months, and this week was no exception. Average planetary A index this week was 20.7, and 23.7 the week before. One day, May 4, was quiet when the planetary A index was only 7. The worst days this week were May 1, when the A index was 40, and May 7, when it was 36.

While these might have been the worst days for HF operators, it was another story for those who enjoy 6 meters. John Reynolds, N7QF, reports from Utah that on May 1 he had a good sporadic-E opening into Oklahoma and Texas. The distance was about 850 miles, and he said most of the people he worked were using 100 W and 3-element Yagis.

A day earlier, Jon Jones, N0JK, worked Argentina on 6 meters from Kansas with E and F2 layer propagation. He says he also worked TI5KD with double-hop E-skip.

Solar flux and sunspot numbers were down this week. Average sunspot numbers were down nearly 40 points from the previous week, and average solar flux was down more than 10 points. Solar flux probably will drop below 100 over the weekend. Solar flux was below 100 only one day in the past month--on April 17--but it dipped just one point below to 99. Predicted solar flux for Friday, May 9, to Monday, May 12, is 95, 95, 100 and 100.

The latest forecast shows planetary A index not going below 20 until May 16. The earth is currently inside a solar wind stream, as it often has been in recent months. An interplanetary shock wave, probably from a coronal mass, hit Earth May 9 at 0500 UTC and should keep conditions active.

Nearly 10 years ago Scott Craig, WA4TTK, released a freeware program for plotting the solar numbers from this bulletin. He calls it the Solar Data Plotting Utility, and it has been improved over the years. The current version runs in Windows and can automatically retrieve data, either from this bulletin or via FTP, from the ARRL. Craig has just posted an updated data file that has daily solar flux and sunspot numbers from January 1, 1989, through April 30, 2003. You can download his software from his Web site.

Another great resource is the NOAA Space Environment Center's Preliminary Report and Forecast, which comes out weekly. It used to be published on paper and mailed, but you can look at it as a PDF file at the SEC NOAA Web site. The current issue, published May 6, has some tables showing predicted solar flux and sunspot numbers until the end of 2007, and smoothed numbers back to January 1998.

Our current solar activity appears to be at around the same level that it was about five years ago. Of course a big difference is that back then the solar activity was increasing, and now it is on the decline. The chart seems to suggest that in 14 months the sunspot count will be about half what it is now. It will drop to about one quarter of the current count in about 25 months.

For more information on propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site.

Sunspot numbers for May 1 through 7 were 171, 175, 134, 172, 144, 117 and 109, with a mean of 146. The 10.7-cm flux was 148.7, 156.5, 147.7, 142, 128.8, 122 and 110.2 with a mean of 136.6. Estimated planetary A indices were 40, 17, 10, 7, 12, 23 and 36, with a mean of 20.7.