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ARRL Propagation Bulletin ARLP027 (2004)

ARLP027 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 27  ARLP027
From Tad Cook, K7RA
Seattle, WA  July 2, 2004
To all radio amateurs 

ARLP027 Propagation de K7RA

Conditions were good for Field Day last weekend.  There wasn't much
of a sunspot count, but there weren't any solar storms either.  I
operated mobile on 20 and 15 meters.  I didn't hear much on 15 in
Seattle, especially on Sunday.  Last week's bulletin suggested
possibly unsettled geomagnetic conditions over the weekend, but
fortunately that was delayed until after Field Day.

A solar wind stream caused geomagnetic indices to begin rising late
Monday UTC (June 28), which is late afternoon here on the West
Coast.  Mid-latitudes weren't affected very much, but the planetary
K index rose to 4.  The planetary A index on Tuesday, June 29 was
20, and the Alaskan College A index (from Fairbanks) was 29.

Sunspot numbers have been dropping.  Average daily sunspot numbers
over the past week were over 55 points below the week before, down
to 60.9.  Average daily solar flux dropped by nearly 19 points.  For
the next week the daily solar flux numbers look to stay about the
same, between 80 and 85, not turning up again until around July 9.
Sunspot numbers and solar flux are expected to peak for the short
term between July 16-19.  Geomagnetic indices should be stable, with
possible unsettled conditions around July 6.

June 30 was the end of the second quarter for 2004.  Time now to
take a look at quarterly averages for solar flux and sunspot
numbers, to help us discern the decline of the current cycle.

The average daily sunspot number for April 1 through June 30 2004
was 71.3, and average solar flux was 99.5.  Both indicators are down
since the first quarter of 2004.

From the third quarter of 2002 through the second quarter of 2004,
the average daily sunspot numbers were 193.5, 152.7, 120.3, 107.3,
110.2, 99.2, 72.9 and 71.3.  The average daily solar flux values for
the same two years were 178.1, 164.2, 134.3, 124.2, 120.8, 137.4,
111.1 and 99.5.  This is another confirmation of cycle 23's slide
toward solar minimum, currently forecast to occur about two and a
half years from now.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at

Sunspot numbers for June 24 through 30 were 94, 83, 64, 48, 45, 50
and 42 with a mean of 60.9.  10.7 cm flux was 108.3, 102.9, 98.9,
97.2, 89.4, 85.1 and 81.8, with a mean of 94.8.  Estimated planetary
A indices were 6, 4, 7, 5, 13, 20 and 10, with a mean of 9.3.
Estimated mid-latitude A indices were 4, 3, 8, 4, 11, 15 and 8, with
a mean of 7.6.


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