ARRL Propagation Bulletin ARLP019 (1997)

ARLP019 Propagation de KT7H

Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, KT7H
Seattle, WA  May 9, 1997
To all radio amateurs

ARLP019 Propagation de KT7H

Geomagnetic conditions became progressively quiet over the week,
after disturbed conditions began the month.  ARLP018 mentioned an
erroneous average A index though, with the actual average as 7, not
49.  The A index this week averaged 9.6.  Solar flux and sunspot
numbers were still the same, stuck in the doldrums with no sign of
increased activity from a new solar cycle.

A new projection from the NOAA Space Environment Service Center
forecasts a smoothed solar flux of 100 for this July, but so far the
predicted values have been increasingly ahead of actual measured
values.  It shows the expected smoothed solar flux for January
through April of this year as 77, 80, 84 and 87, while the actual
monthly averages have been 74, 73.8, 73.5 and 74.5.

The projected smoothed flux for May is 91, but combining the actual
flux for the first eight days of May with subsequent projected
values for the month shows an average of only 71.4, so the gap
between the actual average values versus the projected smoothed
values has grown over January through May from 3, 6.2, 9.5, 12.5 to
19.6.  This same forecast projects a smoothed solar flux of 149 and
sunspot number of 99 one year from now.  One can only hope that
reality will catch up with the projection.

Values for May are expected to stay the same, in the low seventies
for solar flux with minimal sunspot numbers.  Possible disturbances
could appear around May 13 to 21, with the worst periods around the
14th and 15th and the 18th and 19th, and disturbances again around
May 28 and 29.

As the days get longer, expect noise on the lower frequencies to
rise, and less of the good low band propagation that we experienced
on winter nights.  Particularly if we see a rise in solar flux, look
for longer openings to the west on 20 meters in the evening.

Sunspot Numbers for May 1 through 7 were 0, 0, 13, 11, 11, 11 and 11
with a mean of 8.1.  10.7 cm flux was 72.2, 72.1, 71.1, 70.9, 72.3,
72.1 and 72, with a mean of 71.8, and estimated planetary A indices
were 20, 16, 9, 7, 6, 4, and 5, with a mean of 9.6.