ARLP038 Propagation de K7VVV:
September 13, 2002

Propagation Forecast Bulletin 38 ARLP038
From Tad Cook, K7VVV
Seattle, WA September 13, 2002
To all radio amateurs

ARLP038 Propagation de K7VVV

The sunspot count remained fairly high this week, with the numbers still bouncing around over 200. Average daily sunspot numbers rose nearly 15 points this week and solar flux was up by 22. This has been quite an active week geomagnetically. Sunday, Tuesday and Wednesday were quite active, producing impressive aurora displays in northern latitudes. When this happens, polar HF propagation goes away or gets very weak. A year ago at this time the average sunspot numbers were 34 points higher and solar flux was higher by near 42 points.

OK1HH sent an email about the Geophysical Institute Prague showing predicted geomagnetic activity for the upcoming week, and it shows quiet conditions on September 18-19, quiet to unsettled on September 15 and 17, and unsettled on September 13, 14 and 16. Solar flux ranging from 170 to 220 is predicted.

For the next few days NOAA's forecast from the US Air Force shows a planetary A index of 12, 12, 8 and 8 for Friday through Monday, and solar flux at 215, 220, 225 and 220. This forecast shows flux values dipping below 200 by September 22.

WB9SAT writes from Eagar, Arizona about his solar observations. He uses an 8-inch Schmidt-Cassegrain telescope, and says recent sunspots were spectacular. He asked about calculating sunspot numbers at home, and after investigation wrote, "The formula, R=k(10g+f) allows me to accurately estimate the sunspot activity using the point system when viewing the sun."

He goes on to say, "According to NASA, the best way to count the sunspots is to project the sun's image the size of 25 cm (9.84") on a piece of white paper."

He also looked at a number of sites, including,, and

Don't forget the autumnal equinox, which this year is at 0448z on September 23. This is a great time for DX, especially when the geomagnetic field is quiet.

Sunspot numbers for September 5 through 11 were 225, 189, 180, 221, 194, 226 and 213, with a mean of 206.9. 10.7 cm flux was 175.2, 178.1, 182.8, 191.6, 206, 220.5, and 216.1, with a mean of 195.8. Estimated planetary A indices were 10, 10, 45, 26, 10, 24, and 28, with a mean of 21.9.