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ARRL Propagation Bulletin ARLP040 (1997)

ARLP040 Propagation de K7VVV

Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7VVV
Seattle, WA  October 3, 1997
To all radio amateurs

ARLP040 Propagation de K7VVV

Again this week the average solar flux for the previous 90 days rose
two points, and again the daily flux values were above 83, which was
the high average value on Wednesday, the last day of the reporting
week.  Wednesday was the fifty eighty consecutive day that the solar
flux was above the average for the preceding 90 days, and this is a
very positive sign indicating a general upward trend in the new
solar cycle.

This increased activity can have a downside though, and on Wednesday
the geomagnetic field was very unstable, which generally means
higher absorption, especially on high latitude and polar signal
paths.  The planetary A index was 41, and planetary K index went as
high as 6. The A index measured at College, Alaska was 67, and the
highest K index was 8, which means miserable HF conditions.  These
stormy conditions were caused by a flare and a coronal mass ejection
a few days earlier.  For a good explanation of K and A indices, see
the chapter on propagation in any recent edition of the ARRL

Conditions stabilized the next day, and geomagnetic conditions were
very stable, with the Alaska K indices at zero over most of the day,
and worldwide it was mostly one and zero.

Over the next few days look for higher solar activity, with the
solar flux up over 100 around October 7 to 11.  It may dip below 90
after mid month, then rise again to around 90 until November.  Based
on the previous solar rotation, October 25 and 26 may be unstable.
Look for a smaller possibility of geomagnetic instability on October
12 and again on October 15.

Sunspot Numbers for September 25 through October 1 were 50, 40, 33,
23, 27, 25 and 38 with a mean of 33.7.  10.7 cm flux was 88.5, 89.1,
88.4, 87.2, 89.7, 87.7 and 87.1, with a mean of 88.2, and estimated
planetary A indices were 3, 4, 13, 14, 9, 7, and 41, with a mean of

For the VK/ZL/Oceania contest this weekend, here are a few
projections for conditions to that part of the world.

From the center of the continental United States check 80 meters
0630 to 1230z, 40 meters 0600 to 1300z, 20 meters 0300 to 1530z, 15
meters 1930 to 0130z, and 10 meters 2130 to 2330z.

From Southern California, check 80 meters 0630 to 1400z, 40 meters
0600 to 1430z, 20 meters 0300 to 1030z, 15 meters 1900 to 0330z, and
10 meters 2300 to 0130z.

From Texas check 80 meters 0630 to 1230z, 40 meters 0600 to 1300z,
20 meters 0230 to 1100z, 15 meters 1830 to 0200z and 10 meters 2130
to 0030z.

From the Southeast states check 80 meters 0700 to 1200z, 40 meters
0600 to 1230z, 20 meters around 0300z and 1300 to 1500z, 15 meters
with weaker signals around 1900 to 2300z, and possible 10 meter
openings around 2130 to 2300z.

From the New York area check 80 meters 0700 to 1130z, 40 meters 0630
to 1200z, 20 meters possibly around 0400 to 0530z and 1300 to 1530z,
although conditions do not look promising, and 15 meters with only
fair signals from 1930 to 2330z, and a possible opening on 10 meters
from 2000 to 2130z.


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