ZCZC AP12
QST de W1AW
Propagation Forecast Bulletin 12 ARLP012
From Tad Cook, K7VVV
Seattle, WA March 20, 1998
To all radio amateurs
SB PROP ARL ARLP012
ARLP012 Propagation de K7VVV
Solar activity took a big jump over the past week. The solar flux reached 133 on Sunday the 15th, which was the highest since January 5, 1994. Average solar flux for the previous 90 days rose from 94 to 96, and flux values were well above this level on every day this week.
Although Sunday's solar flux was very high, the daily reported value is always for noon in British Columbia. There was a measurement three hours earlier that day when the solar flux was 140.3.
For the next few days look for solar flux to drop to 124, 122 and 116 for Friday through Sunday, and then down to the mid-nineties before the end of the month. Flux levels should go above 100 again by April 6. Possible disturbed days are April 6 through 11, with the worst days around April 6 and 7.
This higher activity is all good news combined with the move into the spring season. Look for longer openings on higher bands, and because the length of the day is similar in northern and southern hemispheres, similar propagation conditions prevail in each hemisphere as well. When solar flux is high, 20 and 15 meters should be best during daylight, and after sundown the best conditions should be on 20 and 40 meters.
Jan Alvestad, the author of the recently mentioned website which compares solar cycles at www.dxlc.com/solar/cyclcomp.html wrote to comment on the material in recent bulletins concerning when the recent cycle actually started. Because the history of solar data collection is relatively short--with only 22 previous cycles--he feels that the best and most objective way to plot the month-by- month cycle progress comparisons is to always start with the minimum between cycles. This is because it is difficult with so few cycles to develop a general definition.
Sunspot Numbers for March 12 through 18 were 114, 115, 119, 110, 92, 81 and 102 with a mean of 104.7. 10.7 cm flux was 101.6, 104.9, 119.6, 133, 123.9, 125.5 and 127, with a mean of 119.4, and estimated planetary A indices were 12, 13, 10, 18, 13, 7, and 4, with a mean of 11.