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27 October, 2007
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.
Source: The
American Radio Relay League
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reports can be found at:
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