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ARRL Propagation Bulletin ARLP044 (2004)

ARLP044 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 44  ARLP044
From Tad Cook, K7RA
Seattle, WA  October 29, 2004
To all radio amateurs 

ARLP044 Propagation de K7RA

This week has been fantastic for HF propagation, with a sun peppered
with spots, and best of all, no geomagnetic upsets. This is an
unusual combination, to have geomagnetic indices so low while
sunspot numbers are up. What could be better, just ahead of the CQ
World Wide DX SSB Contest this weekend?

From last week to this week, the average daily sunspot number more
than doubled, rising over 75 points to 140.7. The sunspot number was
highest on Sunday, October 24 when it was 178. The daily sunspot
number hasn't been this high since late 2003, when it was also 178
on November 30.

I know that last week we were looking forward to the decline toward
solar minimum in a couple of years. But the minimum and maximum are
never determined until long after, when we get a chance to look at
charts of long running moving averages. In between is a great deal
of variation, such as what we are seeing now.

For this weekend, expect great conditions for the DX contest, and
you can expect the higher HF bands to yield plenty. Average solar
flux for this week was about 131, and you can expect continuing
solar flux between 130-135 through the weekend. Saturday, October 30
may have some mildly unsettled geomagnetic conditions, with a
planetary A index of 12. Currently as this bulletin is being
composed late Thursday night U.S. West Coast time, WWV is reporting
a mid-latitude K index of 0.

Several readers sent in articles concerning a new report claiming
there has been more solar activity over the past seven decades than
any time in the previous 8,000 years. You can read about it on the
web at, and

Carl Zelich, AA4MI wrote to tell us about On the home page they post the latest
geophysical alerts and solar flux from WWV, and they have many other
resources. I noticed a link to, where you
can remotely tune and listen to radios all over the world via the

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,

A word about the solar flux numbers for this week. On Monday,
October 25 the observatory in Penticton, British Columbia did not
report a 10.7 cm noon solar flux. Although the local noon (2000z)
measurement is the official daily solar flux, there are also daily
measurements at 1700 and 2300z. We report 141.4 for that day by
averaging the 1700 and 2300z numbers of 139.6 and 143.2.

Sunspot numbers for October 21 through 27 were 112, 134, 141, 178,
146, 124 and 150 with a mean of 140.7. 10.7 cm flux was 112.1,
122.5, 131.6, 140.2, 141.4, 136.7 and 129.5, with a mean of 130.6.
Estimated planetary A indices were 8, 6, 4, 9, 13, 3 and 3, with a
mean of 6.6. Estimated mid-latitude A indices were 5, 5, 1, 6, 9, 0
and 2, with a mean of 4.


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