ZCZC AP32
QST de W1AW
Propagation Forecast Bulletin 32 ARLP032
From Tad Cook, K7RA
Seattle, WA August 6, 2004
To all radio amateurs
SB PROP ARL ARLP032
ARLP032 Propagation de K7RA
Average daily sunspot and solar flux numbers dropped dramatically this week from last. Average daily sunspot numbers were nearly 56 points lower at 42.4, and average solar flux was down over 53 points at 88. Now that we are in the month of August, we can look at July numbers compared to previous months.
Over the past year, October 2003 had the highest monthly average of sunspot and solar flux numbers. Relative to the decline in the solar cycle, the July 2004 numbers were really quite high, no doubt due to the large number of sunspots over a two week period ending around July 26. The numbers for July were higher than for any period since October and November of last year.
The monthly average of daily sunspot numbers, August 2003 through July 2004 were 114.3, 82.6, 118.9, 103, 75.7, 62.3, 75.6, 81, 59.3, 77.3, 77 and 87.8.
The monthly averages of solar flux for the same period were 122.1, 112.2, 155.5, 140.8, 116.1, 114.1, 107, 112.1, 101.2, 99.8, 97.4 and 119.8.
Geomagnetic conditions have been nice and quiet over the past week, with the A index in the low single digits and periods when the K index was 0 at all latitudes. Over this weekend, we could see a rise in geomagnetic activity to unsettled levels. The predicted planetary A index for August 6-10 is 8, 15, 15, 15 and 8.
Solar flux is expected to remain under 100 over the weekend, but slowly rise to a predicted peak around 120 from August 14-19. An increase in activity after August 12 is expected because of the return of sunspot 652, which came into view July 17 during its last transit across the sun, disappearing after July 29. It was squarely facing the earth on July 23, just after the peak in sunspot and solar flux numbers for the month.
Sunspot numbers for July 29 through August 4 were 32, 33, 39, 40, 39, 52 and 62 with a mean of 42.4. 10.7 cm flux was 99.7, 88.7, 86.4, 83.4, 84.5, 87.6 and 85.4, with a mean of 88. Estimated planetary A indices were 9, 7, 9, 8, 8, 5 and 4, with a mean of 7.1. Estimated mid-latitude A indices were 6, 7, 7, 9, 5, 2 and 2, with a mean of 5.4.