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ARRL Propagation Bulletin ARLP029 (1998)

ARLP029 Propagation de K7VVV

Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7VVV
Seattle, WA  July 17, 1998
To all radio amateurs

ARLP029 Propagation de K7VVV

Solar activity was down last week compared to the previous week,
with average solar flux lower by about 15 points and sunspot numbers
down by almost 32 points.  The average solar flux for the previous
90 days was 107, and the flux was below this value on four out of
seven days.  Geomagnetic conditions were quiet to unsettled.  A
solar flare and coronal mass ejection caused the planetary A index
to rise to 37 on Thursday, July 16.  Early in the day the planetary
K index rose to six, which is very bad.

Over the next few days, Friday through Sunday, the planetary A index
is forecast to be 18, 12 and 12, and the solar flux should rise
gradually, from 106 to 107 and finally 108.  Solar flux is expected
to rise above 115 around July 24, then peak between 120 and 125 from
July 26 through the end of the month.  Flux values are expected to
fall below 110 again around August 8.  Look for unsettled
geomagnetic conditions through July 21, and from July 31 until
August 2.  Look for very stable conditions around July 24-28.

Poorer summer HF conditions prevail during the day, but good
worldwide propagation continues on 20 meters in the evening.  The
MUF is higher this year than last, due to higher solar activity, but
it still lags behind what was expected for this point in the cycle.
Perhaps if the solar flux takes another sustained jump upward as it
did after the first of the year, we may see 10 meter openings this
fall.  Currently if 10 is open, it is usually over north-south paths
and only when solar flux has gone higher for a few days.

Some interesting propagation has provided some excitement on six
meters, with contacts this week between Hawaii and a number of
stations in Western North America.  In addition, KG4GC in Cuba was
heard in the northeast United States.

In addition to the failure of the SOHO craft reported recently, the
GOES-9 spacecraft is currently exhibiting severe attitude control
problems.  This is the main craft used to obtain proton, electron,
magnetometer and solar x-ray data.  GOES-8 is being pressed into
service, and soon the GOES-10 satellite will move into position to
take over.

Sunspot Numbers for July 9 through 15 were 61, 91, 96, 82, 50, 58
and 95 with a mean of 76.1.  10.7 cm flux was 114.3, 109.2, 107.7,
99.3, 106.1, 102.9 and 104.8, with a mean of 106.3, and estimated
planetary A indices were 11, 6, 11, 10, 6, 4, and 5, with a mean of


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