ARRL

ARRL Propagation Bulletin ARLP025 (1998)

SB PROP @ ARL $ARLP025
ARLP025 Propagation de K7VVV

ZCZC AP25
QST de W1AW
Propagation Forecast Bulletin 25  ARLP025
From Tad Cook, K7VVV
Seattle, WA  June 19, 1998
To all radio amateurs

SB PROP ARL ARLP025
ARLP025 Propagation de K7VVV

Solar activity over the past week was about the same or slightly
lower than the week previous.  Average sunspot numbers were about
the same and average solar flux was down about eight points.
Geomagnetic activity was stable, except for June 14 when the
planetary K index briefly rose to 5.  Planetary A index for the day
was 15.  Average solar flux for the previous ninety days actually
went down one point to 109, and solar flux over the past week was
below this value on four out of seven days, indicating a flat
trend.

Solar flux is predicted to be about 100 over this weekend, Friday
through Sunday, and the Planetary A index is forecast to be 12, 15
and 8.  Flux values are expected to drop below 100 after June 21,
hit a minimum of 90 on June 26 and 27, and rise above 100 again
after July 2 peaking around 106 on July 5 and 6.  Unsettled
geomagnetic conditions may return around July 1 to 4 and July 7.

Overall conditions for the next few weeks are predicted to be flat,
with no increase in solar activity.  This is based on recurring
conditions observed as the sun goes through a 27.5 day rotation.
Viewing recent solar images on the worldwide web shows few
sunspots, and of the few visible, they seem to be concentrated
outside of the central area that would most affect the earth.

Sunspot Numbers for June 11 through June 17 were 95, 122, 148, 104,
79, 71 and 94 with a mean of 101.9.  10.7 cm flux was 112.4, 112.2,
110.5, 101.9, 100.4, 104 and 100.6, with a mean of 106, and
estimated planetary A indices were 8, 8, 6, 15, 8, 8, and 5, with a
mean of 8.3
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/EX