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ARRL Propagation Bulletin ARLP035 (1997)

ARLP035 Propagation de K7VVV

Propagation Forecast Bulletin 35  ARLP035
From Tad Cook, K7VVV
Seattle, WA  August 29, 1997
To all radio amateurs

ARLP035 Propagation de K7VVV

The past two weeks have been generally good for HF propagation, with
the solar flux above the average (73) for the previous 90 days on
all 14 days.  The solar flux slid to a low of 74.6 on August 20 and
21, then rose to a peak of 83.8 this week on August 26.  Geomagnetic
conditions have been very stable.

Based on the previous solar rotation, solar flux was expected to
drop below 80 at the end of the first week in September, but as this
bulletin is being written it has taken a sudden jump of almost 10
points to 90.5.  The activity is from regions 8076 and 8078, which
are from an older region splitting in two and becoming more active.

The solar flux has not been this high since November 29, 1996, when
there was an exciting flurry of activity that many believed was the
start of solar cycle 23.  The flux rose above 91 on November 23, and
reached a peak of 104.4 two days later.

Conditions should be excellent over the next few days, with solar
flux expected to be in the low nineties through the weekend.
Geomagnetic conditions should be quiet to unsettled, which means a K
index of zero to three.

Based on conditions four weeks earlier, unsettled to active
geomagnetic conditions could hit around September 9 and 10, and
solar flux is expected

Could this be the long awaited start of a real increase in solar
cycle 23?  Let's hope so.  If we can believe the averages for
previous cycles we are surely overdue.  Given the rise in solar flux
and the gradual change toward the Fall season, HF radio conditions
over the next week should be excellent.

Sunspot Numbers for August 14 through 20 were 49, 60, 33, 23, 11, 11
and 11 with a mean of 28.3.  10.7 cm flux was 79.5, 77.7, 77.9,
75.6, 75.8, 74.4 and 74.6, with a mean of 76.5, and estimated
planetary A indices were 17, 8, 9, 9, 6, 5, and 5, with a mean of

Sunspot Numbers for August 21 through 27 were 11, 11, 11, 0, 32, 30
and 33 with a mean of 18.3.  10.7 cm flux was 74.6, 75.5, 76.5,
77.7, 82, 83.8 and 81.9, with a mean of 78.9, and estimated
planetary A indices were 9, 7, 4, 6, 4, 3, and 5, with a mean of


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