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ARRL Propagation Bulletin ARLP009 (2004)

ARLP009 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 9  ARLP009
From Tad Cook, K7RA
Seattle, WA  February 27, 2004
To all radio amateurs 

ARLP009 Propagation de K7RA

A large sunspot emerged over the past week. On February 21 sunspot
564 began to appear around the east limb of the visible solar disk.
By February 23, it was as wide as five planet earths. The sunspot
was rotating across the upper hemisphere of the sun, so it was never
aimed squarely toward earth, but it was most directed toward us on
February 25.

Average daily sunspot numbers were slightly higher this week than
last. Average daily solar flux was exactly the same, or rather lower
by two tenths of a point. Solar activity is rising, and solar flux
should peak between February 28 to March 1 around 130. There is a
sunspot forming currently on the far side of the sun, and it may
cause a slight rise in solar flux around March 8.

Geomagnetic conditions have been very quiet this week. This weekend
is the CQ World Wide 160-Meter SSB Contest. The quality of 160-meter
propagation should depend on how quiet and stable geomagnetic
conditions are. Sunspot 563 released two solar flares on February
26. Earth is expected to encounter a solar wind stream on February
29 or March 1. Planetary A index predictions for February 27 through
March 2 are 12, 12, 15, 20 and 20. Conditions during the 160-meter
contest might be unsettled, especially for stations in the northern
part of North America.

Dave Deatrick, WA8OLD sent an email to remind us of a web site out
of Canada that is useful for information on geomagnetic disturbances
in the northern latitudes. See it at This is part of
the link to Space Weather Canada at
that Steve Burgoyne, VE2OWL sent us last year. It appeared in
Propagation Forecast Bulletin ARLP050 on December 5, 2003. The link
that Dave sent shows a map with a forecast for geomagnetic
disturbances in the Northern United States and across Canada,
through the auroral zone and into the arctic.

Looking back, in this same week last year conditions were nearly
identical to this year. The average sunspot number was 54.9 and
solar flux was 108.8. Look back two years, and the numbers were
quite a bit higher, with sunspot numbers at 189.7 and solar flux at
198.7.  You can find old propagation bulletins back through 1995
along with recent ones at

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the Propagation page on the
ARRL Web site at

Sunspot numbers for February 19 through 25 were 33, 34, 52, 58, 68,
85 and 107 with a mean of 62.4. 10.7 cm flux was 96.4, 95.4, 98.2,
103.9, 104.3, 105.5 and 118.5, with a mean of 103.2. Estimated
planetary A indices were 5, 4, 7, 8, 8, 11 and 8, with a mean of


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