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ARRL Propagation Bulletin ARLP035 (1998)

ARLP035 Propagation de K7VVV

Propagation Forecast Bulletin 35  ARLP035
From Tad Cook, K7VVV
Seattle, WA  August 28, 1998
To all radio amateurs

ARLP035 Propagation de K7VVV

Feel the solar wind?  This has been a very active week for the
geomagnetic field, with solar flares and resulting geomagnetic
storms creating lots of excitement.  On the day that this was
written the planetary A index, which recently has normally been
below 10, was at 112, and 39 the day before.  Currently a major
geomagnetic storm is raging, but conditions are expected to settle
down this weekend.

Solar flux was down slightly from last week and the week before,
while the average solar flux for the previous ninety days rose from
115 to 117.  Solar flux was above these values on every day this
week, indicating a general upward trend.  A year ago the average
solar flux for the week was 78.9, almost fifty points lower than the
current level.  Average sunspot numbers were about 100 points lower.

On August 24 there was a major proton flare.  This caused a major
shortwave fadeout, plus continuing geomagnetic disturbances.  The
flare was big enough to merit reporting in the news wire services.
Reuters reported that the aurora may be strong enough to be visible
across the United States, not just in the northern latitudes.

Conditions such as this are very bad for HF propagation, but create
many interesting VHF contacts via the aurora.  K2SMN in New Jersey
reported working VE2BKL and VE2PEP in Quebec, WA4HEI in Michigan,
and W9JN in Wisconsin, all on two meters.

Look for conditions to calm down this weekend.  Solar flux for
Friday through Sunday is forecast at 135 for all days, and the
planetary A index is predicted to be 30, 15 and 10 over the same
period.  Solar flux is expected to drop down near 115 for September
1 and 2, then peak around 145 around a week later.  There is a
strong possibility of recurrent coronal holes causing geomagnetic
disturbances around September 18 and 19.

The author can be contacted via email at, or via packet

Sunspot Numbers for August 20 through 26 were 120, 138, 102, 121,
99, 109 and 146 with a mean of 119.3.  10.7 cm flux was 138.6,
132.1, 132.9, 126.4, 121.2, 122.1 and 126.9, with a mean of 128.6,
and estimated planetary A indices were 18, 6, 23, 23, 11, 11, and
39, with a mean of 18.7.


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