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ARRL Propagation Bulletin ARLP029 (2004)

ARLP029 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 15, 2004
To all radio amateurs 

ARLP029 Propagation de K7RA

We're putting out this bulletin a day early this week.  K7RA will be
out of town, and Carl Luetzelschwab, K9LA, who often writes the
bulletin in K7RA's absence, is giving a talk on 160-Meter
propagation over the weekend at the Pacific Northwest DX Convention,
near Seattle.  See and specifically for information.

Carl wrote a great piece for the propagation section of the ARRL
Technical Information Service site, which is reached via the URL at
the end of this bulletin.  Titled "Propagation Planning for
DXpeditions," it is good reading for anyone interested in the
practical applications of HF propagation.  The direct link to his
article is,  You will
need Adobe Reader to view the article.

Sunspot numbers and solar flux rose this week.  Average daily
sunspot numbers were up 54 points above last week's average.
Sunspot 649, a big one, came around the sun's eastern limb this
week.  Helioseismic holography shows more sunspots on the far side
of the sun, so the short-term trend for solar activity is up.

Big news is a huge X-class solar flare that was detected at 0140z on
July 15.  If a coronal mass ejection is heading toward earth, it
could mean big geomagnetic storms.  Currently the prediction made
before the flare was for planetary A index of 12, 20, 12 and 10 for
Thursday through Sunday, July 15-18.  Predicted solar flux for the
same period is 140, 140, 135 and 135.

Several readers sent in articles this week about solar storms last
October and how the effects are still being felt at the edge of our
solar system.  The Washington Post ran an article about it last
week, which you can read on the web 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 July 8 through 14 were 17, 32, 58, 98, 118, 129
and 149 with a mean of 85.9.  10.7 cm flux was 81.8, 86.7, 93.3,
104.4, 125, 149.5 and 138.1, with a mean of 111.3.  Estimated
planetary A indices were 5, 5, 8, 14, 13, 16 and 9, with a mean of
10.  Estimated mid-latitude A indices were 1, 4, 5, 13, 12, 11 and
6, with a mean of 7.4.


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