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ARRL Propagation Bulletin ARLP042 (2004)

ARLP042 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 42  ARLP042
From Tad Cook, K7RA
Seattle, WA  October 15, 2004
To all radio amateurs 

ARLP042 Propagation de K7RA

Solar activity has been very low. In fact, on October 10-11, Sunday
and Monday, the sunspot count was 0. Images of the sun for those
days show a blank, spotless sun. You can see those images on the website. Just check the archive section by
dialing in the dates on the upper right of the web page, and look at
the sun images on the left.

October 10-11 were the first days with a sunspot count of 0 since
January 27-28, 2004. Before that to find another day with a 0
sunspot number, you have to go back six years to January 7-9, 1998.
There was one day prior to that with a 0 sunspot number, October 23,
1997, and there were several 0 days in the summer of that year.

As we look back further, we are closer to the bottom of the previous
sunspot cycle. The minimum must have been eight years ago, because
the longest string of 0 sunspot days that I can find in recent
history is September 13 to October 20, 1996, a very quiet 38
continuous days of no activity.

We can look back at the propagation bulletins published during that
time and see the reports on week after week of no sunspots (check
the archive at I see that it was in
this week in 1996 in Propagation Forecast Bulletin ARLP042 that we
first began regular weekly reporting of the geomagnetic A index.
Robert Wood, WB5CRG, who is now W5AJ, suggested this. Looking at
these reports perhaps gives us a view of what conditions will be
like two years from now.

For the next week and through the end of the month, daily solar flux
is expected to hover around 90. A solar wind stream from a recurring
coronal hole may cause some unstable geomagnetic conditions today
and tomorrow, October 15-16. Geomagnetic conditions are expected to
be very quiet for the week of October 22-28.

More email arrived this week with reports of band conditions,
particularly 10-meters. Alain, F5LIW reports that every afternoon
around 1700-1800z he works South America on 10-meters. At 1747z on
October 7 Alain worked LU3XD in South Argentina. LU3XD used 100
watts and a dipole. The following day at 1723z, Alain worked HF0QF
in the South Shetlands with S9 reports at both ends. He reports that
every evening 10-meters seems quiet, but when he calls CQ, he works
overseas stations. He uses 100 watts and a tri-band Yagi.

If you would like to comment or have a tip, email the author at

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 October 7 through 13 were 38, 28, 24, 0, 0, 14
and 41 with a mean of 20.7. 10.7 cm flux was 93.8, 90.6, 88, 89,
86.9, 87.6 and 88.5, with a mean of 89.2. Estimated planetary A
indices were 4, 7, 6, 8, 11, 11 and 35, with a mean of 11.7.
Estimated mid-latitude A indices were 4, 4, 3, 5, 9, 7 and 17, with
a mean of 7.


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