QST de W1AW
Propagation Forecast Bulletin 20 ARLP020
From Tad Cook, K7VVV
Seattle, WA May 11, 2001
To all radio amateurs
SB PROP ARL ARLP020
ARLP020 Propagation de K7VVV
As sunspots fade from view, solar flux and sunspot numbers are down. Average sunspot numbers for the week declined by nearly 45 points, and average solar flux was off by over 40 points. A and K indices went high this week, indicating a minor geomagnetic storm on May 9 and 10. This began on May 8 when the earth entered a high speed solar wind stream. The interplanetary magnetic field, which is another name for the sun's enormous magnetic field, turned south on May 9. This rendered the earth's magnetosphere vulnerable to gusts of solar wind.
Active geomagnetic conditions are fading, and should become unsettled on May 11 and 12, with planetary A indices of 15 and 12, dropping to around 10 on May 13 and 14. Contesters should see fairly good conditions for the CQ-M Contest this weekend. Solar flux is expected to stay near 135 for the next few days, then rise above 150 after May 17 and above 175 after May 19.
Currently we are moving from spring toward summer propagation conditions. 10 meters is not as viable as it was in late March, and as longer daylight hours in the northern hemisphere heat the ionosphere, the ionosphere thins and the MUF is lower during daylight hours. 15 meters can still be quite good, especially into areas that are dark, and as the days become longer, night time openings on 20 meters will become more common.
For the CQ-M International DX Contest this weekend, we have some path projections to several targets in the former Soviet Union, including Asiatic Russia (UA0), European Russia (UA1), and Ukraine (UR).
Sunspot numbers for May 3 through 9 were 157, 186, 151, 120, 103, 88 and 98 with a mean of 129. 10.7 cm flux was 172.3, 175.6, 160.6, 155, 138.3, 128.7 and 129.4, with a mean of 151.4, and estimated planetary A indices were 7, 9, 5, 7, 17, 14 and 32 with a mean of 13.