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ARRL Propagation Bulletin ARLP046 (2005)

ARLP046 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 46  ARLP046
From Tad Cook, K7RA
Seattle, WA  November 4, 2005
To all radio amateurs 

ARLP046 Propagation de K7RA

Conditions recovered from zero sunspots, which lasted for five days.
Average sunspot numbers rose nearly 10 points to 17.6 this week.
Average daily solar flux only rose 1.2 points to 75.4.

October just ended, so let's look at monthly averages for sunspot
numbers and solar flux to see if the trend is still down.  Last
month we looked at quarterly averages, but with monthly averages
this time we'll see more volatility.

The average daily sunspot numbers for the months September 2004
through October 2005 were 50, 77.9, 70.5, 34.7, 52, 45.4, 41, 41.5,
65.4, 59.8, 68.7, 65.6, 39.2 and 13.  Average daily solar flux for
the same months was 103, 106, 113.7, 95, 102.3, 97.2, 89.9, 85.9,
99.5, 93.7, 96.5, 92.4, 91.9 and 76.6.

You can see that the numbers declined every month for the past four
months, especially October, which was like dropping off a cliff.

There has been some geomagnetic disturbance over the past couple of
days, but conditions should settle down for the ARRL CW Sweepstakes
this weekend.  The predicted planetary A index for Friday through
Monday, November 4-7 is 20, 20, 12 and 8.  Sunspot numbers and solar
flux should rise slightly, reaching a peak around November 6-8.

If the planetary A index is 20 or higher this weekend it may cause
some difficulty reaching those VE8 or KL7 multipliers in
Sweepstakes, but don't count on any major flare activity.

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at, An archive of past
bulletins is found at,

Sunspot numbers for October 27 through November 2 were 0, 0, 11, 14,
29, 33 and 36 with a mean of 17.6. 10.7 cm flux was 71.6, 73.1,
74.1, 75.6, 77.8, 77.3, and 78, with a mean of 75.4. Estimated
planetary A indices were 6, 5, 2, 5, 13, 8 and 6 with a mean of 6.4.
Estimated mid-latitude A indices were 5, 4, 1, 3, 6, 7 and 5, with a
mean of 4.4.


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