ARRL

ARRL Propagation Bulletin ARLP037 (1999)

SB PROP @ ARL $ARLP037
ARLP037 Propagation de K7VVV

ZCZC AP37
QST de W1AW  
Propagation Forecast Bulletin 37  ARLP037
From Tad Cook, K7VVV
Seattle, WA  September 10, 1999
To all radio amateurs 

SB PROP ARL ARLP037
ARLP037 Propagation de K7VVV

Solar flux numbers were disappointing this week, with levels not
this low since April.  Solar flux dropped to 106.8 on Wednesday, and
the average flux for the week was down over 80 points from last
week.  This seems very disappointing as we head toward the fall
equinox.  Solar flux is expected to stay low for the next few days,
with levels at 105, 100 and 100 for Friday through Sunday.
Planetary A indices of 15, 15 and 12 are predicted for the same
period, so geomagnetic conditions should be unsettled as well.

Solar flux should be back to 140 by September 16, 170 around
September 18, and over 200 around September 20.  Flux is expected to
peak at 220 from September 22-24.  The most unsettled geomagnetic
conditions are expected around September 15-16 and 26-27.

The URL that KF7E sent for last week's bulletin ARLP036 was missing
a letter on the end.  It really should have read
http://space.rice.edu/ISTP/justdials.html.  Actually the URL he sent
was fine, but somehow justdials.html got changed to justdials.htm
when the bulletin was written.  Check it out.  It shows data from
the Advanced Composition Explorer Spacecraft, presented by the
Department of Space Physics and Astronomy from Rice University.

Sunspot numbers for September 2 through 8 were 134, 116, 103, 101,
81, 111 and 111 with a mean of 108.1.  10.7 cm flux was 156.5,
139.3, 131.2, 121.8, 118.5, 112.4 and 106.8, with a mean of 126.6,
and estimated planetary A indices were 11, 18, 15, 8, 6, 17 and 9,
with a mean of 12.

For the path projection for this week, we will do an exercise
comparing 10-20 meters for this weekend over a couple of paths with
the same paths for September 23, when solar flux should be higher
and we are closer to the equinox.  The paths will originate in
Arizona between Phoenix and Tucson, and end in New Zealand and
Japan.

For this weekend, to New Zealand, 20 meters 0300-1100z, 17 meters
0000-0630z, 15 meters 1900-0530z, 12 meters 2000-0300z and 10 meters
2130-0130z.  To Japan, 20 meters 0400-0730z, 17 meters 2030-0600z,
15 meters 2100-0400z, 12 meters 2230-0100z, 10 meters possibly
2230-0000z.

For September 23 to New Zealand, 20 meters 0330-1530z, 17 meters
0200-1730z, 15 meters around the clock, best signals 0600-1100z,
weakest 1300z and 2100-2200z, 12 meters 1800-1000z (weak
2030-2230z), and 10 meters 1830-0900z, stronger toward the end of
the period.  To Japan, 20 meters 0500-1700z, 17 meters all hours,
best 0730-1430z, weakest 2130-0030z, 15 meters 1430-1800z and
1930-0800z, 12 meters 2030-0600z, and 10 meters 2030-0530z.

As you can see, the rising solar flux and changing season should
make a big difference for propagation on the upper bands.
NNNN
/EX