ARRL

ARRL Propagation Bulletin ARLP044 (2007)

SB PROP @ ARL $ARLP044
ARLP044 Propagation de K7RA

ZCZC AP44
QST de W1AW  
Propagation Forecast Bulletin 44  ARLP044
From Tad Cook, K7RA
Seattle, WA  October 26, 2007
To all radio amateurs 

SB PROP ARL ARLP044
ARLP044 Propagation de K7RA

Zero, zero, zero sunspots for 18 straight days now.  A single
sunspot appeared briefly October 6-7, no sunspots for four days
prior, one sunspot for the final few days of September, and none for
the three whole weeks prior to that.

Until recently, many of us thought the solar cycle minimum occurred
in March of this year.  You can see a table of projected smoothed
numbers with a minimum in March 2007 at, http://tinyurl.com/27j2fs.

This year we began looking at a table of 3-month sunspot number
averages, and for a while the data seemed to support a March
minimum.  But then we hit this longer period of no sunspots, and the
3-month average dropped again.  You can see the most recent table in
Propagation Forecast Bulletin ARLP041 at,
http://www.arrl.org/w1aw/prop/2007-arlp041.html.  Note the 10.2
average assigned to August (which is the middle of the July through
September period the 3-month average is based on) is lower than
March, which was 11.2.

With such a long period of so few sunspots, at the beginning of
November we might see a much lower 3-month average.  This is because
the sum of all the daily sunspot numbers from August 1 until now is
only 492, and if we still see no sunspots through next Wednesday,
that total divided by the number of days for
August-September-October (92) is only 5.4.

So how low is 5.4, compared to the last solar minimum?  I looked at
averages between December 1995 and April 1997, and the only time the
3-month average of sunspot numbers dipped below 10 was in 1996, with
9.9 in March and 8.7 in September:

Dec 95 16.7
Jan 96 14.7
Feb 96 13.1
Mar 96  9.9
Apr 96 10.9
May 96 13.0
Jun 96 14.6
Jul 96 17.5
Aug 96 12.4
Sep 96  8.7
Oct 96 10.2
Nov 96 14.2
Dec 96 16.4
Jan 97 11.7
Feb 97 11.3
Mar 97 16.4
Apr 97 22.6

But this doesn't really tell us when solar activity will increase,
just that we are currently seeing lower overall sunspot activity
than we did at the last solar minimum eleven years ago.

With no sunspots, it is sometimes amazing what hams can work on the
air.  Geomagnetic activity increased on October 25 due to solar
wind, and just ahead of that Dick Hanna, K3VYY of Beaver Falls,
Pennsylvania worked two Florida stations on 28.37 MHz at 0100z,
which was two and a half hours after his local sunset.  This is an
unusual time for propagation over this path, which would normally
occur during the middle of the day with the sunspot number over 100.

Jon Jones, N0JK of Wichita, Kansas reported some good E-layer skip
on 6 meters for around 2 hours on October 20, beginning at 0115z.
He worked VE3DXP/W7 in Las Vegas, and K7ICW was also loud from New
Mexico.  He also heard some double-hop E-skip from Washington State
and Florida.  Jon commented that E-skip is rare in October.

During an hour at lunch on October 25, Chip Margelli, K7JA reported
from Southern California, "10 meters opened up from California to
Europe and Africa for the first time in a very long time.  Besides
the loud Caribbean stations, CT1CJJ, CU2AF, GM3POI, MM0SJH, CU3EQ,
C52C, and 5H3EE were great finds on 28 MHz between 1900-2000z." K7SS
in Seattle reported that mid-day West Coast time, he heard C52C on
10 meters and heard K7RI work him.

This weekend is the CQ World Wide DX Phone Contest, and geomagnetic
activity should calm by the start of the event. Predicted planetary
A index for October 26-31 is 20, 12, 10, 15, 10 and 8.  Geophysical
Institute Prague predicts unsettled to active conditions October 26,
unsettled October 27, quiet to unsettled October 28, unsettled
October 29-30, quiet to unsettled October 31, and quiet conditions
on November 1.

You can get 45 day planetary A index and solar flux predictions at,
http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html.  A new one is
issued daily after 2100z, but often there is a delay before the link
to the new forecast is posted.  To get around this, after 2100z if
the link to that day's forecast hasn't appeared, try changing the
URL for the previous day's forecast to what it would be for the
current date.  For instance, the URL for the October 25 forecast was
at, http://www.swpc.noaa.gov/ftpdir/forecasts/45DF/102545DF.txt.
After 2100z on October 26, if the link to the latest forecast hasn't
appeared, change the URL to,
http://www.swpc.noaa.gov/ftpdir/forecasts/45DF/102645DF.txt and see
if it is available yet.

Thomas Giella, KN4LF of Lakeland, Florida reports that he has a
propagation forecast available.  You can learn about it at,
http://www.kn4lf.com/kn4lf6.htm.

If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL
Technical Information Service at,
http://www.arrl.org/tis/info/propagation.html. For a detailed
explanation of the numbers used in this bulletin see,
http://www.arrl.org/tis/info/k9la-prop.html. An archive of past
propagation bulletins is at, http://www.arrl.org/w1aw/prop/. Monthly
propagation charts between four USA regions and twelve overseas
locations are at, http://www.arrl.org/qst/propcharts/.

Sunspot numbers for October 18 through 24 were 0, 0, 0, 0, 0, 0 and
0 with a mean of 0.  10.7 cm flux was 68.2, 67.3, 66.9, 67.2, 66.7,
67.1, and 67.5 with a mean of 67.3. Estimated planetary A indices
were 10, 15, 12, 4, 5, 7 and 3 with a mean of 8. Estimated
mid-latitude A indices were 11, 11, 8, 5, 3, 6 and 2, with a mean of
6.6.
NNNN
/EX