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ARRL Propagation Bulletin ARLP031 (2000)

ARLP031 Propagation de K9LA

QST de W1AW  
Propagation Forecast Bulletin 31  ARLP031
From Carl Luetzelschwab, K9LA
Ft Wayne, IN  August 4, 2000
To all radio amateurs 

ARLP031 Propagation de K9LA

Tad K7VVV, your regular solar reporter, is on vacation this week.
This report was submitted by Carl, K9LA.

Solar activity for last week (July 28 - August 3) was mostly at low
levels.  A minor M-class flare from region 9090 occurred on July 28.
Several new regions (9110, 9111, 9112, 9113, 9114, and 9115) emerged
later in the week.  Region 9114 produced a C7 flare and associated
CME on August 2.

The 10.7 cm solar flux, following the sun's 27-day rotation period,
decreased to a minimum of about 155 at the beginning of last week.
Solar flux is forecasted to steadily climb to a maximum of about 240
around mid-August.  A comment about 10.7 cm solar flux - although
10.7 cm solar flux is easy to measure because the Earth's atmosphere
is transparent at that wavelength, energy at 10.7 cm is about 1
million times less energetic than the true ionizing energy.  Thus
10.7 cm solar flux contributes nothing to the formation of the
ionosphere.  But it is an indicator of the general activity level of
the sun, and smoothed solar flux values (a 12 month running average)
correlate very well with smoothed sunspot numbers (SSN).

Solar activity for next week (August 4 - August 10) is expected to
be at moderate to high levels.  Isolated M-class flares are
expected, along with a chance for an isolated major flare.

Historically the equinox months (September and March) give us the
greatest amount of magnetic storms due to the orientation of the
Earth at these times with respect to the solar wind.  Thus expect an
increase in storms up to mid-September, then a gradual decrease
after that to a minimum in December.

Cycle 23 continues its march upward, with a peak forecasted by the
end of the year.  For details, see the web site referenced in last
week's bulletin (  The
latest SSN data is 113 for January 2000.  The estimated SSN for the
month of August is 120.  Cycle 23 appears to be similar to, but just
a bit higher than, Cycle 20, which peaked at an SSN of 110.  This
level of activity, while not approaching that of Cycles 22 and 21,
will still give us excellent conditions on the higher HF bands as we
progress from Summer to Fall and into Winter.

Sunspot numbers for July 27 through August 2 were 174, 163, 183,
138, 123, 139 and 153 with a mean of 153.3. 10.7 cm flux was 162.4,
157.8, 153.2, 149.9, 147.9, 149.4 and 150.6, with a mean of 153, and
estimated planetary A indices were 9, 30, 27, 10, 19, 15 and 14,
with a mean of 17.7.


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