ARRL

ARRL Propagation Bulletin ARLP053 (2006)

SB PROP @ ARL $ARLP053
ARLP053 Propagation de K7RA

ZCZC AP53
QST de W1AW  
Propagation Forecast Bulletin 53  ARLP053
From Tad Cook, K7RA
Seattle, WA  December 22, 2006
To all radio amateurs 

SB PROP ARL ARLP053
ARLP053 Propagation de K7RA

More of the stormy space weather appeared this week, while at the
same time sunspot activity was lower. Average daily sunspot numbers
dropped 17 points to 10.4 for the week of December 14-20. But on
December 15, the planetary A index, an indicator of global
geomagnetic activity from magnetometers around the globe, rose to
104, a very high number indicating a severe geomagnetic storm.

The cause was a large coronal mass ejection that happened to be
earth-directed. It arrived on December 14, and caused Aurora
Borealis appearing as far south as Arizona. During the hours of
darkness in North America between December 14-15, the planetary K
index rose to 8 for three successive three-hour periods. That is
very big. For the next few weeks, you can view the numbers for that
period at, http://www.sec.noaa.gov/ftpdir/indices/DGD.txt.

Thanks to N7SO and N7TP for the tip on a paper presented last week
in San Francisco at the Fall 2006 meeting of the American
Geophysical Union. The paper was titled "Geomagnetic activity
indicates a large amplitude for sunspot cycle 24," and you can read
the abstract at, http://tinyurl.com/yjzy3q. The longer article is
at, http://tinyurl.com/yewboz.

The paper proposes that the next sunspot cycle could be one of the
most intense cycles ever observed. The prediction technique uses
geomagnetic activity during solar minimum to predict solar activity
during the peak of the next cycle. But the geomagnetic activity used
for this calculation isn't the dramatic sort that we've seen this
week, but constant levels of solar wind streams that frequently
affect the earth's magnetosphere. NASA has an article on this at,
http://science.nasa.gov/headlines/y2006/21dec_cycle24.htm.

Another article concerning the upcoming cycle 24 that you shouldn't
miss is "The World Above 50 MHz" column in the current (January
2007) issue of QST. This is the second half of the same column from
the December 2006 issue.

Last week's intense geomagnetic activity produced some nice auroral
propagation on 6 meters. Jon Jones, N0JK was operating portable atop
a parking garage in Salina, Kansas using a 2-element Yagi and
running 30 watts. On December 15 at 0015z, he worked K9MU in
Chippewa Falls, Wisconsin, who was quite strong on SSB, over 500
miles away. Later at 0225z he heard KL7NO in Fairbanks working
stations in 9-land. Fairbanks is about 2,800 miles from Salina. By
the way, I calculated those distances quickly using ZIP codes with a
handy utility at,
http://www.melissadata.com/Lookups/zipdistance.asp.

Jeff Hartley, N8II of Shepherdstown, West Virginia sent in some
interesting observations on the 10-meter contest of two weeks ago
and aurora propagation from last week. First, regarding the 10-meter
contest, he indicated he worked 1,400 stations using "only" a
5-element monoband 10-meter Yagi at 98 feet, which is three full
wavelengths above ground.

Jeff continues, "There was stable propagation (possibly F2) to NM
and El Paso, TX Sunday and a pipeline into AZ/NV. I probably worked
a record number of NM, OK, KS, and IA stations during this year's
event (latter 3 worked via plentiful Es). Worked EA8 (several and
loud), 5H, 3X, S9SS, ZS on Sat AM and we had a very nice but only
2.25 hour long F2 West Coast opening starting around 1700z. Sunday
it lasted longer, but CA was very weak and spotty and the Pacific NW
was in and out, peaking at beginning and end of opening. A35RK
called Sunday afternoon and biggest surprise was a Es to F2 link QSO
with KH6NI at 0219z Sunday (ZL1CN was worked via same about 0120z).
All states were worked except AK and ND and there certainly was prop
to ND."

He goes on to say, "The aurora starting around 0000z on the 15th was
intense on 6M, but died out after 1 hour. It or auroral E probably
returned later, but I was whipped. Signals peaked approximately NW
and propagation favored that direction. Stations were heard from IA
to VE2 and the beacons from MI and OH at one point were as loud as
S9. There was not enough CW activity and a lot of guys just can't
copy SSB sigs well with the phase distortion at 50 MHz."

Currently we've seen several days of 0 sunspots. Expect little or no
sunspots for the short term, and a planetary A index on December
22-27 of 15, 15, 10, 5, 5 and 15. The next predicted period of
higher geomagnetic activity is around January 2, with a planetary A
index of 25.

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 December 14 through 20 were 23, 19, 20, 11, 0, 0
and 0 with a mean of 10.4. 10.7 cm flux was 93.4, 87.1, 82.3, 81.3,
74.7, 72.9, and 71.5, with a mean of 80.5. Estimated planetary A
indices were 63, 104, 11, 4, 8, 14 and 24 with a mean of 32.6.
Estimated mid-latitude A indices were 30, 48, 10, 3, 7, 9 and 16,
with a mean of 17.6.
NNNN
/EX