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ARRL Propagation Bulletin ARLP002 (2004)

ARLP002 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 2  ARLP002
From Tad Cook, K7RA
Seattle, WA  January 9, 2004
To all radio amateurs 

ARLP002 Propagation de K7RA

Average daily sunspot numbers rose slightly this week and solar flux
was down a bit. Except for January 2, geomagnetic conditions were
active. The prediction for the next few days, January 9-11, was for
moderate geomagnetic conditions, but this seems to be changing with
the arrival of energy from a couple of coronal mass ejections.
These were sent into space on January 6 and 7, and there is a small
possibility of a larger solar flare over the next day or so.

As this bulletin is being written after 1000z on January 9, the
mid-latitude K index has risen to 5 for the 0900z reading, as
reported on WWV. It is no coincidence that the interplanetary
magnetic field points south, leaving earth vulnerable.

Earth's active geomagnetic field could stabilize over the next
couple of days, but is expected to become unsettled to active again
around January 12-13. January 14-15 are expected to be quiet, with a
stable geomagnetic field.

Solar flux is expected to rise slowly over the next few days,
reaching 130 by January 13, then possibly peaking around 135 from
January 19-21.

On January 4 the earth reached perihelion, the closest point to the
sun in our orbit. It was closest around 0900z, about 91.7 million
miles from the sun. Last July 4 was aphelion, when sun and earth
were furthest apart, a little over 94.8 million miles. This means
that assuming all other factors are equal, radiation from the sun
was about 7% more intense on January 4 than it was on July 4.

The nights are still long, although getting shorter as we slowly
advance toward spring. 160, 80 and 40 meters will be good at night
with lower noise levels than summer, when days are longer. Long
distance communication on 80 meters is probably best when both ends
of the path are in darkness.

For instance, from the east coast to Europe, 80-meter propagation
should improve after sundown in the United States and fade around
sunrise at the other end. Similarly, from the west coast to Japan,
80-meters should open after dark at the Japan end and fade around
sunrise on the west coast.

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 1 through 7 were 47, 51, 65, 80, 80, 78
and 93 with a mean of 70.6. 10.7 cm flux was 116, 116.5, 116.1,
119.4, 123, 117.3 and 118.8, with a mean of 118.2. Estimated
planetary A indices were 27, 13, 26, 24, 22, 20 and 32, with a mean
of 23.4.


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