ARLP053 Propagation de KT7H: December 20, 1996

Propagation Forecast Bulletin 53 ARLP053
From Tad Cook, KT7H
Seattle, WA December 20, 1996
To all radio amateurs

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.