ARLP029 Propagation de K7RA:
July 15, 2004

Propagation Forecast Bulletin 29 ARLP029
From Tad Cook, K7RA
Seattle, WA July 15, 2004
To all radio amateurs

ARLP029 Propagation de K7RA

We're putting out this bulletin a day early this week. K7RA will be out of town, and Carl Luetzelschwab, K9LA, who often writes the bulletin in K7RA's absence, is giving a talk on 160-Meter propagation over the weekend at the Pacific Northwest DX Convention, near Seattle. See and specifically for information.

Carl wrote a great piece for the propagation section of the ARRL Technical Information Service site, which is reached via the URL at the end of this bulletin. Titled "Propagation Planning for DXpeditions," it is good reading for anyone interested in the practical applications of HF propagation. The direct link to his article is, You will need Adobe Reader to view the article.

Sunspot numbers and solar flux rose this week. Average daily sunspot numbers were up 54 points above last week's average. Sunspot 649, a big one, came around the sun's eastern limb this week. Helioseismic holography shows more sunspots on the far side of the sun, so the short-term trend for solar activity is up.

Big news is a huge X-class solar flare that was detected at 0140z on July 15. If a coronal mass ejection is heading toward earth, it could mean big geomagnetic storms. Currently the prediction made before the flare was for planetary A index of 12, 20, 12 and 10 for Thursday through Sunday, July 15-18. Predicted solar flux for the same period is 140, 140, 135 and 135.

Several readers sent in articles this week about solar storms last October and how the effects are still being felt at the edge of our solar system. The Washington Post ran an article about it last week, which you can read on the web at,

For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service propagation page at,

Sunspot numbers for July 8 through 14 were 17, 32, 58, 98, 118, 129 and 149 with a mean of 85.9. 10.7 cm flux was 81.8, 86.7, 93.3, 104.4, 125, 149.5 and 138.1, with a mean of 111.3. Estimated planetary A indices were 5, 5, 8, 14, 13, 16 and 9, with a mean of 10. Estimated mid-latitude A indices were 1, 4, 5, 13, 12, 11 and 6, with a mean of 7.4.