[LeArc] ARLP034 Propagation de K7VVV

[Joseph L. Rossmiller]

SB PROP @ ARL $ARLP034
ARLP034 Propagation de K7VVV

ZCZC AP34
QST de W1AW =20
Propagation Forecast Bulletin 34  ARLP034
>From Tad Cook, K7VVV
Seattle, WA  August 16, 2002
To all radio amateurs=20

SB PROP ARL ARLP034
ARLP034 Propagation de K7VVV

The sun shows renewed activity this week. There was a dip in solar flux =
and sunspot numbers centered around August 6-8, but with the appearance =
of giant sunspot number 69 and more than 10 smaller groups, the indices =
are again on the rise. Mean daily sunspot numbers were up 9.3 points =
this week over last, and average daily solar flux rose by precisely the =
same amount. Solar flux reached a recent peak of 241.5 on July 26, =
dropped over 100 to 134.6 on August 8, and may peak again above 240 =
around the middle of next week.

Geomagnetic numbers over the past week indicated unsettled to active =
conditions, and this is expected to continue. On August 14 a coronal =
mass ejection appeared that wasn't squarely earth-directed, but there is =
a fair chance it will cause upset on earth. The predicted planetary A =
index for August 16-18 is 30, 15 and 10, and there is a 10 to 20% chance =
of a severe geomagnetic storm.

Bob, NM7M had some comments concerning K3MIY's recent email about =
heating and thinning of the ionosphere. Bob says that the summer =
seasonal reduction in Maximum Usable Frequency isn't caused by heating, =
but by a chemical difference in the F-layer during summer. Bob wrote:

"It is really a chemical effect due to the differential lifting of =
atomic oxygen with seasons, as compared to that of molecular nitrogen =
and oxygen. The (n2+O2)/O ratio is greater in summer than winter, =
increasing by 1.5X to 3.3X from 150 km to 400 km.

"The higher ratio means more recombination of electrons (with NO2+ ions) =
than production of electrons by photo-ionization of atomic oxygen, the =
principal constituent of the F-region. That lowers the MUF in the =
summer.

"Check it out with MINIPROP, taking a path from W7 to EU, summer and =
winter."

Bob says this is covered in greater detail on page 55 of his book, =
"Little Pistol's Guide to HF Propagation."

KN4LF passed along the URL for his web site, http://www.kn4lf.com and =
points out that he has a page concentrating on Medium Frequency =
propagation at http://www.kn4lf.com/kn4lf5.htm.  N0JK from Kansas wrote =
saying that the summertime E-layer skip on 6 meters hasn't been very =
productive, but August 4 was fantastic. He said 6 meters was open from =
the Midwest to the Caribbean and northern South America from 2000z to =
after 2330z. 9Y4TL, CO8DM and ZF1DC made hundreds of 6 meter contacts, =
and ZF1DC even made a few 2 meter contacts to the U.S.

Sunspot numbers for August 8 through 14 were 150, 164, 140, 180, 230, =
214 and 254, with a mean of 190.3. 10.7 cm flux was 134.6, 140.1, 148.4, =
172.3, 183.9, 191.8, and 208.1, with a mean of 168.5. Estimated =
planetary A indices were 10, 15, 16, 15, 15, 13, and 15,
with a mean of 14.1.

NNNN
/EX




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