ARLP026 Propagation de K7RA:
June 27, 2003

Propagation Forecast Bulletin 26 ARLP026
From Tad Cook, K7RA
Seattle, WA June 27, 2003
To all radio amateurs

ARLP026 Propagation de K7RA

This week had somewhat quieter geomagnetic conditions compared to the previous week, but average daily solar flux was down a bit and average daily sunspot numbers remained about the same. Recent projections anticipate no truly quiet periods ahead.

ARRL Field Day is this weekend, and I wish the geomagnetic conditions could be better. The predicted planetary A index for Friday through Monday is 20, 25, 20 and 20. Although an A index of 25 for Saturday doesn't look very promising, this prediction is made several days prior, and like weather forecasts, the real conditions could be different. In addition, a planetary A index of 20 or 25 doesn't guarantee a radio blackout on the high frequencies.

Just to run some numbers for this weekend, using W6ELprop (download free from for Saturday with a path from California to Ohio, a solar flux of 125 and K index of 4, we see 20-meters opening on Saturday morning before the start of Field Day and continuing a good path through the day. Around 2330z the path may be unreliable, then it comes back a lot stronger at 0100z. This is just as 40-meters is starting to open. Both bands stay strong through the night until local sunrise in California. 80-meters opens after sunset in California, and fades after sunrise in Ohio. The path opens on 20-meters around 1430z.

David Moore of Morro Bay, California wrote in with a tip about an interesting article that details some new findings regarding the mechanics of the solar cycle. The article reports research suggesting slowly moving circulating currents of compressed gasses 125,000 miles into the sun's interior influence the production of sunspots. The article also says that the speed of these circulating currents of gasses varies from cycle to cycle, and the fast circulation in the last cycle suggests the next cycle should be strong, peaking around 7 or 8 years from now. You can read the article at

Still more reports arrived about the VHF openings around June 17. Jake Groenhof, N0LX wrote to say he was on Mount Evans in Colorado and using one half watt on 2-meter SSB when he worked a station 850 miles away in California. He went up to 5 watts and worked five more Californians. He has a web page detailing this at

Ward Silver, N0AX wrote to say that the description in last week's bulletin of the A index being linear was incorrect. The related K index is logarithmic, but the A index is a larger scale, and not linear.

Sunspot numbers for June 19 through 25 were 108, 121, 118, 94, 104, 131, and 115, with a mean of 113. 10.7 cm flux was 122.9, 116.9, 115, 110.2, 113.5, 114.5, and 116.3, with a mean of 115.6. Estimated planetary A indices were 18, 12, 23, 16, 20, 31, and 19, with a mean of 19.9.