ARRL

ARRL Propagation Bulletin ARLP020 (2004)

SB PROP @ ARL $ARLP020
ARLP020 Propagation de K7RA

ZCZC AP20
QST de W1AW  
Propagation Forecast Bulletin 20  ARLP020
From Tad Cook, K7RA
Seattle, WA  May 14, 2004
To all radio amateurs 

SB PROP ARL ARLP020
ARLP020 Propagation de K7RA

Sunspot activity has been in the doldrums, expected for this stage
of the declining solar cycle. Average daily solar flux and sunspot
numbers hardly changed from last week to this week. Now both numbers
are rising modestly due to quickly expanding sunspot 606, now
squarely aimed at earth.

There is also some good news from the sun's far side, where
helioseismic holography detects another sizable sunspot group. Both
sunspot and solar flux numbers are now over 100. The lowest recent
sunspot count was 30 on May 6, and solar flux went down to 85 the
following day.

Solar flux values should rise over this weekend, with the Friday
through Monday (May 14-17) solar flux predicted at 105, 110, 115 and
115. Solar flux should stay around 115 through May 20. The predicted
planetary A index indicates unsettled conditions for Saturday, May
15, with the Friday through Monday planetary A index predicted at
12, 15, 12 and 8.

A new issue of the NOAA Space Environment Center Preliminary Report
and Forecast has some solar cycle predictions on pages 12-13. The
forecast for the bottom of the cycle still looks to be around the
end of 2006 or early 2007. You can read about it at,
http://www.sec.noaa.gov/weekly/pdf/prf1497.pdf. Since this is in PDF
format, you will need Acrobat Reader to view it.

For the higher HF bands, declining sunspots mean fewer or no
openings on 15, 12 and 10 meters, and probably a greater reliance on
20 or 17 meters for worldwide propagation during daylight hours.

Sunspot numbers for May 6 through 12 were 30, 34, 37, 57, 55, 46 and
83 with a mean of 48.9. 10.7 cm flux was 86.4, 85.2, 87.2, 93.2, 93,
90.2 and 98.8, with a mean of 90.6. Estimated planetary A indices
were 8, 17, 10, 6, 7, 10 and 11, with a mean of 9.9.  Estimated
mid-latitude A indices were 10, 13, 7, 3, 5, 8 and 9, with a mean of
7.9.
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