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ARRL Propagation Bulletin ARLP042 (1997)

ARLP042 Propagation de K7VVV

Propagation Forecast Bulletin 42  ARLP042
From Tad Cook, K7VVV
Seattle, WA  October 17, 1997
To all radio amateurs

ARLP042 Propagation de K7VVV

Judging from the high solar flux and sunspot activity over a month
ago, recently we expected to see more of that same activity, since
the Sun rotates relative to Earth once every 27.5 days.
Unfortunately by the time the rotation was complete, most of those
active regions were gone.

This week we saw solar activity up only by a little.  On five out of
seven days the solar flux was above the average for the previous
ninety days.  Geomagnetic activity was up a lot though over last
weekend, when the Estimated Planetary K Index was up to six over
several periods.  This is a very high value, indicating very stormy
conditions with high absorption of radio signals.

The most recent forecast indicates a small rise in solar flux into
the low nineties next week, peaking around October 22 and 23, then
dropping back to the mid-eighties before the end of the month.  In
November look for unsettled to active geomagnetic conditions around
the 5th and 6th.

The NOAA Space Environment Center reported that a panel of solar
experts met recently and fixed the probable date for the recent
solar minimum around October, 1996, with a possible range from May
through December.  Panelists believe that Cycle 23 should be a large
cycle, but not as big as Cycle 19 in the late nineteen fifties.
They expect it to peak around March, 2000, with a range from June,
1999 to January, 2001.  This places the peak in the very near
future, but sunspot cycles go up much faster than they go down.

Sunspot Numbers for October 9 through 15 were 27, 44, 31, 60, 44, 44
and 47 with a mean of 42.4.  10.7 cm flux was 83.5, 84.2, 86.1,
88.7, 88.3, 84.8 and 86.9, with a mean of 86.1, and estimated
planetary A indices were 19, 27, 26, 7, 7, 5, and 4, with a mean of


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