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ARRL Propagation Bulletin ARLP037 (1997)

ARLP037 Propagation de K7VVV

Propagation Forecast Bulletin 37  ARLP037
From Tad Cook, K7VVV
Seattle, WA  September 12, 1997
To all radio amateurs

ARLP037 Propagation de K7VVV

The rise in solar activity continues, and this past week on Monday
solar flux values peaked at 119.4.  The last time the solar flux was
above this value was January 27, 1994.  On the same Monday the
sunspot number was 101, which has been unequaled since September 3,
1994.  We are definitely through the minimum and on the upswing of
the next solar cycle.

The average solar flux for the previous 90 days rose another two
points this past week (to 77), as it had the previous week.
September 11 was the 38th consecutive day that the flux was above
the 90 day average.  Along with this greatly increased activity has
been some geomagnetic disturbances.  The most disturbed period over
this past week was around 0600 to 0900 UTC on September 9.

Recent projections from the NOAA Space Environment Service Center
show the solar flux dropping below 100 after September 17, then back
above 100 around September 26, and above 115 after October 4.  These
estimates are based upon the previous solar rotation, so new active
regions on the Sun could send these numbers higher.  This new
activity means that long distance propagation is now possible on the
upper HF bands, where prior to this 20 meters was the primary band
for worldwide propagation.

Check 15 and even 10 meters, where openings are now possible,
especially over north to south paths.  Combined with the progression
toward the Fall equinox, conditions now and over the next month
should be the best seen in several years.

Sunspot Numbers for September 4 through 10 were 56, 79, 85, 84, 97,
101 and 95 with a mean of 85.3.  10.7 cm flux was 93, 96, 97.6, 102,
119.4, 116.1 and 114.9, with a mean of 105.6, and estimated
planetary A indices were 19, 5, 7, 3, 9, 19, and 19, with a mean of


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