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ARRL Propagation Bulletin ARLP004 (2004)

ARLP004 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 4  ARLP004
From Tad Cook, K7RA
Seattle, WA  January 23, 2004
To all radio amateurs 

ARLP004 Propagation de K7RA

Average daily sunspot numbers and solar flux rose modestly this
week, with sunspot numbers up nearly 4, and solar flux rising by 9
points. Last week's bulletin reported that we were entering a solar
wind, and the effects can be seen in the planetary A index for last
Friday, shown at the bottom of this bulletin. Geomagnetic indices
were down by Saturday. On Monday, January 19, energy from a coronal
mass ejection hit earth, but only caused high geomagnetic activity
at high latitudes. For the 19th and 20th the planetary A index was
only an unsettled 17 and 16, but the College A index in Fairbanks,
Alaska was 37 on both days.

A strong solar wind from another coronal mass ejection hit earth at
0130z on January 22 causing a strong geomagnetic storm. The
mid-latitude Fredericksburg A index as reported by NOAA was 35, and
the mid-latitude A index as reported by WWV was 46. The College A
index on January 22 was 80, and planetary A index was 62.

Another coronal mass ejection should hit earth on January 23 or 24,
although latest projections on Thursday show a predicted planetary A
index for January 23-26, Friday through Monday at 25, 15, 15 and 10.
The Prague Geophysical Institute predicts a minor geomagnetic storm
for January 23, unsettled to active conditions for January 24,
unsettled conditions on January 25, quiet to unsettled conditions
for January 26, and active geomagnetic conditions on January 27 and

Users of the WA4TTK Solar Data Plotter (available free at can see the prominent rise in
sunspot numbers and solar flux at the end of October 2003. The lower
frame, showing a detailed plot of activity over the past eight
months shows the October peak followed by the declining activity
from the same sunspot group over the following solar rotations.

With several sunspot groups rotating off the visible disk, solar
flux over the next few days should decline from 120 down to 110. It
should rise again after January 26-27 for another short-term peak
around the end of the first week of February. displayed a fantastic photo of a giant filament of
hot gas rising above the sun, taken by Gary Palmer of Los Angeles on
January 21. See it at .

Vern Rabin of Colorado took another photo of the same filament,
which can be viewed at .

The beacon network operated by the IARU and the Northern California
DX Foundation hasn't been mentioned here in a long time. The 18
beacon stations operate all over the world on 20, 17, 15, 12 and 10
meters, and are a good tool for gauging propagation. Details are at . The NCDXF website lists many
software tools for use with the beacon network at . There are programs
that work on many platforms in addition to current and recent
versions of Windows, including DOS, Linux, OS/2, Windows 3.1 and
Palm Pilot.

This weekend is the CQ Worldwide 160-meter CW Contest. Conditions
for the contest might be good if geomagnetic conditions don't cause
havoc. VHF conditions might not be disturbed if a geomagnetic storm
occurs, and this weekend is the ARRL January VHF Sweepstakes. In
addition, the British Amateur Radio Teledata Group is sponsoring
their 2004 RTTY Sprint Contest this weekend.

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

Sunspot numbers for January 15 through 21 were 57, 68, 56, 72, 87,
94 and 104 with a mean of 76.9. 10.7 cm flux was 119.1, 120.3,
122.6, 119.5, 134.6, 128.9 and 130.1, with a mean of 125. Estimated
planetary A indices were 16, 26, 14, 18, 17, 16 and 12, with a mean
of 17.


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