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ARRL Propagation Bulletin ARLP036 (2005)

ARLP036 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 36  ARLP036
From Tad Cook, K7RA
Seattle, WA  August 26, 2005
To all radio amateurs 

ARLP036 Propagation de K7RA

This was a big week for geomagnetic storms, or rather one huge storm
mid week.  On August 24 a large coronal mass ejection struck earth,
and the resulting geomagnetic storm stimulated bright aurora
borealis visible as far south as Utah and Colorado.

The energy for all this emerged from fast-growing sunspot 798, which
released two M-class solar flares on August 22.  The planetary K
index actually got up to 9 on August 24, and the planetary A index
reached 110.  The solar flux on the day of the flare rose nearly 60
points to 157.3, a big number for this part of the solar cycle.

During the same hour that one of the flares erupted, Ray Bass, W7YKN
of Sparks, Nevada, reported an HF radio blackout.  He wrote, ''Forty
meters appeared to have died for about an hour.  Only one local
station about five miles away, W6FHZ, could be heard.  Even WWV and
WWVH were very weak here in Sparks, Nevada''.

Solar activity should be low for the next few days, and geomagnetic
conditions quiet.  Predicted solar flux for Friday, August 26
through the following Monday is 95, 95, 90 and 90.  Predicted
planetary A index for those same days is 15, 8, 8 and 10.

Last week we mentioned some links to sites showing 6 meter E layer
propagation over a number of years, all shown cumulatively by day of
the year.  This gives us some idea of what times of the year are
best for this.  Robert Mobile, K1SIX of New Hampshire has a web page
with many more of this type of chart over many paths.  See it at

A reader sent in an article from NASA about advances in space
weather forecasting.  You can see it at

Finally, let's take time to note the passing of Phil Klass, who
died August 9 at the age of 85.  Although I don't think Phil was
ever a ham, he is credited with coining the term ''avionics'' as an
aviation journalist, and he was an editor of Aviation Week and Space
Technology.  I had the pleasure of his acquaintance, and subscribed
to his newsletter for many years.  The newsletter and his many
wonderful books covered his research into aerial optical phenomena
and how this and human error often were behind reports of objects in
the air which otherwise could not be identified.  A couple of nice
obituaries are linked from and

If you would like to comment or have a tip, 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 August 18 through 24 were 42, 61, 74, 77, 85, 55
and 87 with a mean of 68.7.  10.7 cm flux was 82.7, 93.1, 98.1, 98.5,
157.3, 112.3 and 98.6, with a mean of 105.8.  Estimated planetary A
indices were 16, 7, 5, 8, 12, 9 and 110 with a mean of 23.9.
Estimated mid-latitude A indices were 9, 6, 2, 5, 7, 7 and 72, with
a mean of 15.4.


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