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15 September, 2007
The Sun has been blank, with no visible sunspots, for the past seven
days, September 7-13. We may not see another sunspot until September 22,
just before the Autumnal Equinox.
Thursday evening, September 13, Spaceweather.com
(http://www.spaceweather.com)
mentioned a coronal wind hitting earth this evening, September 14. The
IMF points south, which makes earth vulnerable to solar wind, but other
sources don't call for an increase in geomagnetic activity today.
We might assume that a solar wind from 27 to 28 days ago could return
at this time, based on the rotation of the Sun relative to earth. But
looking back four weeks on,
http://www.sec.noaa.gov/ftpdir/indices/quar_DGD.txt
does not reveal any heightened activity. Of course, it could be that the
Interplanetary Magnetic field pointed north, protecting earth from the
coronal wind.
U.S. Air Force Space Weather Operations predict continued quiet geomagnetic
conditions, with a planetary A index for September 14 at 8, then 5 every
day through September 20. Geophysical Institute Prague predicts quiet
to unsettled conditions September 14-15 and quiet conditions September
16-20.
Each month we are checking the Preliminary Report and Forecast of Solar
Geophysical Data from NOAA SEC for updates to the forecast for this sunspot
cycle. The current edition is at 1671, dated September 12, at http://www.sec.noaa.gov/weekly/index.html.
Compare the table of predicted smoothed sunspot numbers on page 9 with
number 1666 dated August 7. Note the latest forecast has a more pronounced
minimum, all centered around March and April 2007.
Floyd Clowning, K5LA and Eva Tupis, W2EV sent in some information on
PropNET (see http://propnet.org/),
the automated network of low power BPSK stations dedicated to detecting
propagation paths on 160, 30, 10, 6 and 2 meters, and plotting them on
maps. This was mentioned briefly in Propagation Forecast Bulletin ARLP015
about five months ago.
The PropNET website has all the information on setting up one of these
stations, and of course, you don't have to be a participant to use it.
All the data that is generated appears on the web site.
One thing PropNET needs is more overseas participation. The network currently
gives good propagation indicators in the United States, but could sure
use a few stations outside North America.
Check the October 2007 issue of QST for an interesting article concerning
the bottom of this solar cycle by Steve Ford, WB8IMY. Titled "Waiting
for the Sun," Steve gives us ideas on how to best utilize the available
propagation when there are few sunspots.
Finally, Ken Fletcher of the British DX Club sent in a link to
http://www.solarcycle24.com/,
a neat site devoted to the current and upcoming sunspot cycles.
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 September 6 through 12 were 12, 0, 0, 0, 0, 0 and
0 with a mean of 1.7. 10.7 cm flux was 66.7, 67.1, 66.6, 66.7, 66.9, 66.1,
and 65.9 with a mean of 66.6. Estimated planetary A indices were 13, 12,
6, 2, 2, 2 and 2 with a mean of 5.6. Estimated mid-latitude A indices
were 8, 10, 3, 2, 2, 2 and 2, with a mean of 4.1.
Source: The
American Radio Relay League
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