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ARRL Propagation Bulletin ARLP032 (2004)

ARLP032 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 32  ARLP032
From Tad Cook, K7RA
Seattle, WA  August 6, 2004
To all radio amateurs 

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

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.


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