ARRL Propagation Bulletin ARLP045 (2004)

ARLP045 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 45  ARLP045
From Tad Cook, K7RA
Seattle, WA  November 5, 2004
To all radio amateurs 

ARLP045 Propagation de K7RA

The quiet geomagnetic conditions and big sunspots of last week
couldn't last forever, and unfortunately there was some geomagnetic
upset on Saturday, October 30, the first day of the CQ World Wide DX
Phone weekend. Conditions weren't terrible, although higher latitude
and polar paths were more difficult.

A huge sunspot (693) emerged the day before the contest, October 29,
and it moved into position for greatest effect on earth around
November 2-3. Another sunspot (696) is moving into prime
earth-facing position over the next day or two. A coronal mass
ejection from sunspot 696 blasted into space on November 4, and the
energy from that event is expected to hit us late November 5 or on
November 6. The predicted planetary A index for November 5-8 is 15,
30, 25 and 15. The predicted solar flux for those same days is
around 140. This is a little higher than it has been over the past
week. This week average daily sunspot numbers dropped a little less
than two points to 139. Average daily solar flux rose four points to

This weekend is the ARRL Sweepstakes CW Contest. With active
geomagnetic conditions predicted for Saturday, it could be a bit
rough. High latitude and polar paths are affected most. Since this
isn't a DX contest, propagation over the poles isn't much concern,
but working VE8 and KL7 multipliers could be a bit rough. We hope it
is more moderate than the current prediction, but the prediction is
for higher A and K indices than last weekend.

Now that October has passed, we can calculate and compare monthly
averages of daily sunspot numbers and solar flux, perhaps to see
some trends. Although both measures were up slightly in October,
this solar cycle continues to decline.

The monthly average of daily sunspot numbers, October 2003 through
October 2004 were 118.9, 103, 75.7, 62.3, 75.6, 81, 59.3, 77.3, 77,
87.8, 69.6, 50 and 77.9.

The monthly averages of daily solar flux for the same period were
155.5, 140.8, 116.1, 114.1, 107, 112.1, 101.2, 99.8, 97.4, 119.8,
110, 103 and 106.

If you would like to comment or have a tip, email the author at,

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,

Sunspot numbers for October 28 through November 3 were 150, 130,
153, 163, 144, 110 and 123 with a mean of 139. 10.7 cm flux was
133.4, 128.8, 136.4, 139.2, 135.5, 133.1 and 135.9, with a mean of
134.6. Estimated planetary A indices were 3, 7, 17, 10, 5, 4 and 10,
with a mean of 8. Estimated mid-latitude A indices were 2, 6, 10, 7,
4, 2 and 7, with a mean of 5.4.