QST de W1AW
Propagation Forecast Bulletin 9 ARLP009
From Tad Cook, K7RA
Seattle, WA February 27, 2004
To all radio amateurs
SB PROP ARL ARLP009
ARLP009 Propagation de K7RA
A large sunspot emerged over the past week. On February 21, sunspot 564 began to appear around the east limb of the visible solar disk. By February 23, it was five times as large as Earth. The sunspot was rotating across the upper hemisphere of the sun, so it was never aimed squarely toward earth, but it was most directed toward us on February 25.
Average daily sunspot numbers were slightly higher this week than last. Average daily solar flux was lower by 0.2 point. Solar activity is rising, and solar flux should peak between February 28 to March 1 at around 130. A sunspot currently is forming on the far side of the sun, and it may cause a slight rise in solar flux around March 8.
Geomagnetic conditions have been very quiet this week. This weekend is the CQ World Wide 160-Meter SSB Contest. The quality of 160-meter propagation should depend on how quiet and stable geomagnetic conditions are. Sunspot 563 released two solar flares on February 26. Earth is expected to encounter a solar wind stream on February 29 or March 1. Planetary A index predictions for February 27 through March 2 are 12, 12, 15, 20 and 20. Conditions during the contest might be unsettled, especially for stations in the northern latitudes of North America.
Dave Deatrick, WA8OLD, of Sault Ste Marie, Michigan, reminded us of a Canadian Web site that offers information on geomagnetic disturbances in the northern latitudes. This is part of Space Weather Canada. The link that WA8OLD sent shows a map with a forecast for geomagnetic disturbances in the Northern US and across Canada, through the auroral zone and into the Arctic.
During this week one year ago, conditions were nearly identical to this year's. Average sunspot number was 54.9 and solar flux was 108.8. Going back two years, the numbers were quite a bit higher, with sunspot numbers at 189.7 and solar flux at 198.7. Archived propagation bulletins from 1995 through the present are available on the ARRL Web site.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site.
Sunspot numbers for February 19 through 25 were 33, 34, 52, 58, 68, 85 and 107, with a mean of 62.4. The 10.7 cm flux was 96.4, 95.4, 98.2, 103.9, 104.3, 105.5 and 118.5, with a mean of 103.2. Estimated planetary A indices were 5, 4, 7, 8, 8, 11 and 8, with a mean of 7.3.