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ARRL Propagation Bulletin ARLP004 (2005)

ARLP004 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 4  ARLP004
From Tad Cook, K7RA
Seattle, WA  January 28, 2005
To all radio amateurs 

ARLP004 Propagation de K7RA

Solar activity was down this week. Average daily sunspot numbers
were off by nearly 36 points to 53.4, and average daily solar flux
dropped 31 points to 101.7. Last Friday, January 21, we were hit by
a big blast of energy from an X7 class solar flare on the previous
day. Just one point below two days earlier, the planetary A index
went to 61 and the mid-latitude A index was 30, also one point

A severe geomagnetic storm lasted the next couple of days, but
conditions really calmed down on Monday through Thursday (January
24-27) of this week. On Wednesday, January 26, the mid-latitude A
index went clear down to 0, because the K index upon which it is
based was 0 during all eight reporting periods. This is incredibly
quiet, and good for HF propagation, at least if the sunspots are
around to support it.

We could hope for similar quiet conditions for this weekend's CQ
World Wide 160-Meter CW Contest, but the forecast doesn't look that
great. The predicted planetary A index for Friday through Monday,
January 28-31 is 15, 30, 20 and 20. This isn't due to any flare, but
earth is about to move into a solar wind stream, and the most active
conditions are expected on Saturday. Conditions should be back to
quiet by February 3.

Ken Kopp, KK0HF of Topeka, Kansas sent in a great article that
appeared in the Baltimore Sun on recent solar activity. It is full
of dramatic descriptions of solar flares, the recent giant sunspot,
and the evacuation of astronauts on the International Space Station
to the better-shielded Russian Zvezda service module. For a while at
least, you may be able to read it (without having to register) by
clicking on the following link on,,1,7436903,pr

Also be sure to check out a constantly updated collection of links
to press clippings relating to amateur radio on Ken's web site at

Flares, solar wind and geomagnetic storms aren't bad for all radio
propagation. 6-meters often gets interesting during active
conditions, and a number of reports arrived this week concerning

When HF operators thought their radios were dead on January 21,
OZ1DJJ in Denmark worked K1TOL on 6-meter CW during Aurora in the
Scandinavian Activity Contest. You can hear the QSO at Click to the left of the
phrase, "I am so lucky!!" Thanks to Arne, SM7AED for passing that

Jon Jones, N0JK reported a nice 6-meter opening between Arizona and
the Midwest on January 21 beginning at 0015z and lasting nearly four
hours. Jon was mobile in Wichita, Kansas and talked to K7TOP on
6-meters. K7NN in Tucson and AC7XP and K7TOP in Phoenix worked
stations in Kansas, Missouri, Oklahoma, Texas and Tennessee with
strong signals.

And finally, ever thought of building your own magnetometer? I've
thought for a long time that in addition to noting the College K
index, Boulder K index or planetary K index, it would be neat to
have one that is strictly local. Where I live in Seattle, I could
have a University District K index, although in the city it might be
affected by passing trucks. Check a web page devoted to just such an
instrument at You can see current
real time results from a homebrew magnetometer in the Netherlands at

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 January 20 through 26 were 61, 69, 60, 40, 42,
56 and 46 with a mean of 53.4. 10.7 cm flux was 122.7, 113.5, 102.2,
95.8, 94.6, 94.1 and 89.3, with a mean of 101.7. Estimated planetary
A indices were 12, 61, 28, 17, 6, 4 and 4 with a mean of 18.9.
Estimated mid-latitude A indices were 10, 30, 23, 12, 5, 2 and 0,
with a mean of 11.7.


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