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ARRL Propagation Bulletin ARLP050 (2003)

ARLP050 Propagation de K7RA

Propagation Forecast Bulletin 50  ARLP050
From Tad Cook, K7RA
Seattle, WA  December 5, 2003
To all radio amateurs

ARLP050 Propagation de K7RA

Geomagnetic conditions have been quite stable this week, and as a
result, HF propagation has been good. Right now the earth is
entering a solar wind stream, which could trigger auroras. The
interplanetary magnetic field is currently pointing south, which
means earth is vulnerable to the effects of solar wind.

The current forecast is for geomagnetic indices to rise over the
next few days. The predicted planetary A index for Friday through
Monday, December 5-8 is 20, 35, 25 and 20. Predicted solar flux for
those same days is 115, 110, 105 and 105. Solar flux values are
predicted to run between 105 and 110 and then reach a slightly lower
minimum around December 12, then rise again toward a short-term peak
around December 18-22.

Petr Kolman, OK6MGW is predicting active geomagnetic conditions for
December 10-11, unsettled to active on December 5 and 9, unsettled
conditions on December 6 and quiet to unsettled conditions on
December 7-8.

Conditions this weekend during the ARRL 160-Meter CW contest will be
affected by any geomagnetic disturbance. Check WWV at 18 minutes
after the hour (or check the WWV text at at 0018, 0318, 0618,
0918, 1218, 1518, 1818, and 2118z for the latest mid-latitude K

If the value is 3 or less, conditions should be good. Right now
conditions don't look very promising, with the mid-latitude K index
at 0600z on Friday, December 5 at 5. WWV is reporting an A index of
6, but that is really based on all the K indices for December 4.
Otherwise, that would be quite good.

As an example of how different these values are, if the K value of 5
were measured during an entire UTC day, the resulting A index for
that day would be 48. An A index of only 6 indicates K indices for
the day between 1 and 2.

Diane Leveque, NH6HE sent in a news item from NASA this week
concerning openings in the earth's magnetic field detected by NASA's
IMAGE (Imager for Magnetopause-to-Aurora Global Exploration)
satellite. You can read the story on the NASA.GOV web site at or at
the SCIENCE.NASA.GOV web site at

This story is of interest to amateur radio operators because
openings in the magnetic field allow solar wind to pass through,
affecting earth. The IMAGE satellite is the first spacecraft
dedicated to imaging the earth's magnetosphere, and NASA has a
fascinating web page for IMAGE at

David Moore also sent an article from on outbursts of
gas from the sun, which is at,

And finally, Stephane Burgoyne, VE2OWL of Drummondville, Quebec sent
in a truly wonderful link recently at, which provides a unique view and
forecast of geomagnetic conditions in northern latitudes.

Stephane's own web site is at,, in French.

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 November 27 through December 3 were 154, 185,
177, 178, 159, 119 and 100 with a mean of 153.1. 10.7 cm flux was
174.7, 167.7, 165.9, 152.8, 143.3, 139.3 and 123.8, with a mean of
152.5. Estimated planetary A indices were 10, 10, 9, 10, 10, 9 and
7, with a mean of 9.3.


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