ZCZC AP25
QST de W1AW
Propagation Forecast Bulletin 25 ARLP025
From Tad Cook, K7VVV
Seattle, WA June 19, 1998
To all radio amateurs
SB PROP ARL ARLP025
ARLP025 Propagation de K7VVV
Solar activity over the past week was about the same or slightly lower than the week previous. Average sunspot numbers were about the same and average solar flux was down about eight points. Geomagnetic activity was stable, except for June 14 when the planetary K index briefly rose to 5. Planetary A index for the day was 15. Average solar flux for the previous ninety days actually went down one point to 109, and solar flux over the past week was below this value on four out of seven days, indicating a flat trend.
Solar flux is predicted to be about 100 over this weekend, Friday through Sunday, and the Planetary A index is forecast to be 12, 15 and 8. Flux values are expected to drop below 100 after June 21, hit a minimum of 90 on June 26 and 27, and rise above 100 again after July 2 peaking around 106 on July 5 and 6. Unsettled geomagnetic conditions may return around July 1 to 4 and July 7.
Overall conditions for the next few weeks are predicted to be flat, with no increase in solar activity. This is based on recurring conditions observed as the sun goes through a 27.5 day rotation. Viewing recent solar images on the worldwide web shows few sunspots, and of the few visible, they seem to be concentrated outside of the central area that would most affect the earth.
Sunspot Numbers for June 11 through June 17 were 95, 122, 148, 104, 79, 71 and 94 with a mean of 101.9. 10.7 cm flux was 112.4, 112.2, 110.5, 101.9, 100.4, 104 and 100.6, with a mean of 106, and estimated planetary A indices were 8, 8, 6, 15, 8, 8, and 5, with a mean of 8.3