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ARRL Propagation Bulletin ARLP024 (2004)

ARLP024 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 24  ARLP024
From Tad Cook, K7RA
Seattle, WA  June 11, 2004
To all radio amateurs 

ARLP024 Propagation de K7RA

Solar activity remains low. As the sunspot cycle declines, we are
inevitably headed toward a year or two of quiet sun. The sunspot
minimum is several years off, however.

This week average daily sunspot numbers were up slightly by over 7
points to 68.3. Average daily solar flux was down nearly 10 points
to 87.4. Geomagnetic conditions remained quiet to slightly

The chance of any geomagnetic upset this weekend seems very remote.
The sun is nearly blank, but today two sunspots peeked around to the
visible face. Solar flux is expected to remain low, declining to
around 80 next week. Solar flux is expected to rise above 100 once
again between June 19-22.

Regional Warning Center Prague (
predicts quiet geomagnetic conditions on June 13, 14 and 17, quiet
to unsettled conditions on June 12, and unsettled conditions on June
11, 15 and 16. On June 9, the sun spewed a coronal mass ejection,
but the energy was aimed away from earth. It caused no geomagnetic

Remember that in all this, what most HF operators will want is more
sunspots and higher solar flux, but low geomagnetic A and K indices.
Note that geomagnetic conditions are much quieter than they were for
many months, when it seemed that solar flares and geomagnetic storms
would never stop.

Reader David Moore passed along an interesting article on sources of
solar hazards in interplanetary space. Read it on the web 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 June 3 through 9 were 77, 55, 59, 60, 82, 72 and
73 with a mean of 68.3. 10.7 cm flux was 90, 89.4, 84.5, 88.4, 88.5,
86 and 85.2, with a mean of 87.4. Estimated planetary A indices were
8, 11, 11, 11, 8, 9 and 14, with a mean of 10.3.  Estimated
mid-latitude A indices were 6, 14, 8, 12, 7, 6 and 13, with a mean
of 9.4.


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