ARRL

ARRL Propagation Bulletin ARLP053 (1996)

SB PROP @ ARL $ARLP053
ARLP053 Propagation de KT7H

ZCZC AP73
QST de W1AW
Propagation Forecast Bulletin 53  ARLP053
From Tad Cook, KT7H
Seattle, WA  December 20, 1996
To all radio amateurs

SB PROP ARL ARLP053
ARLP053 Propagation de KT7H

Solar activity is up again with the return of region 7999.  Average
flux was up this week by 13 points, the sunspot numbers up over 17
points, and A index up 1 point.

Flux is expected to rise up to around 96 on December 23, then drop
below 80 on December 31, then up to the mid-eighties again around
January 5 and 6.  Expect the A and K indices to be up again around
January 6, 11 and 12.

Sometimes there are questions about the effect of a solar or lunar
eclipse on propagation.  I'll include here some notes from Dave
Palmer which present some interesting thoughts about eclipses:

''Solar and Lunar eclipses do not represent anything special in
terms of planetary positions.  They're really just a matter of
perspective.

Solar eclipses occur only at the New Moon, when the Moon is between
the Earth and Sun. Lunar eclipses happen only at Full Moon, when
the Earth is between the Moon and Sun.

But Full/New Moon happens about every 28 days. The reason we don't
get eclipses (on Earth, at least) twice a month is that the Moon's
''orbit about the Earth'' is tilted, and the coincidence of an exact
line-up of the Sun-Moon-Earth (as seen from some spot on Earth)
happens only a couple times per year.

However, every New Moon, there IS a solar eclipse out in space
either north or south of the Earth, and every Full Moon, there's a
Lunar eclipse north or south of the Moon (OK, really, there's a
solar eclipse SOMEWHERE in space for as long as the Moon is not
obscured by the Earth, and a Lunar eclipse for as long as the Moon
is totally obscured by the Earth). The point is that the eclipse's
shadow usually just misses hitting the Earth (or the Moon)''.

Sunspot Numbers for December 12 through 18 were 32, 31, 30, 25, 27,
38 and 33, with a mean of 30.9.  10.7 cm flux was 81.1, 81.7, 82.5,
85, 86.2, 86.4 and 88.4, with a mean of 84.5.  Planetary A indices
for the same period were 8, 6, 5, 10, 10, 8, and 5, with a mean of
7.4.
NNNN
/EX