[South Florida DX Association] ARLP049 Propagation de K7RA

Fri Dec 10 19:10:52 EST 2010

SB PROP @ ARL $ARLP049
ARLP049 Propagation de K7RA

ZCZC AP49
QST de W1AW
Propagation Forecast Bulletin 49  ARLP049
 From Tad Cook, K7RA
Seattle, WA  December 10, 2010
To all radio amateurs

SB PROP ARL ARLP049
ARLP049 Propagation de K7RA

Average daily sunspot numbers for the week were up over nine points, to 
35, and average solar flux rose over six points to 87.3. These 
differences compare the dates December 2-8 with the previous seven days. 
Average planetary A index declined 2.5 points to 2.1, while average 
mid-latitude A index dropped 1.1 points to 1.6. These are nice numbers, 
with higher sunspot numbers accompanied by lower geomagnetic indices.

Predicted solar flux for the near term is right near or slightly above 
the average for the past week, at 87, 87, 88, 88, and 88 for December 
10-14. Predicted planetary A index for December 10-14 is 8,
10, 10, 8 and 5.  Planetary A index is expected to remain around 5 from 
December 15-24.

Geophysical Institute Prague has a slightly different prediction for the 
next seven days.  They predict unsettled conditions for December 10-11, 
quiet to unsettled December 12, unsettled December 13, quiet December 14 
and quiet to unsettled December 15-16.

Note the period of somewhat unsettled geomagnetic activity centers 
around this weekend, the dates for the ARRL 10 Meter Contest, December 
11-12.  But only a mild increase in geomagnetic activity is expected.  
The Geminid meteor shower peaks December 13-14, and could provide some 
ionized trails enhancing 10 meter propagation.

This year's 10 meter contest is the first time that Mexican states will 
be counted as multipliers along with U.S. states and Canadian provinces, 
as well as DXCC countries. You can see a map of the 32
Mexican states in PDF format at 
http://www.dxxe.org/concurso/xe-mults.pdf.  Complete contest rules are 
at http://www.arrl.org/10-meter.

Ten meters offers many opportunities for working Mexico from other North 
American locations this weekend. For instance, Distrito Federal, which 
includes Mexico City, should be workable from Salt
Lake City from 1730-1900z, and possibly from 1700-2100z.  The path from 
the San Francisco Bay Area looks even better, with the possibility of 
strong signals from 1700-2130z. From the Chicago
area, a likely opening is 1700-1830z, possibly open as early as 1630z 
and as late as 2000z. From Ohio the path looks good 1630-1930, extending 
possibly 30 minutes early and an hour later. From
Winnipeg, Manitoba (VE4) the possibilities look excellent 1730-1900z, 
very good 1630-2030, and possibly extending to 1600-2100z.

If you want to use the predicted smoothed sunspot number with a 
propagation prediction program for this month or next, you can find the 
latest predicted values in the table on page 11 in issue
PRF-1840 at http://www.swpc.noaa.gov/weekly.  The values are updated 
there about every 4-5 weeks.

You can also do a peek into the future, as this table shows a predicted 
smoothed sunspot number for December 2010 of 38, 74 in December 2011, 
and 89 in December 2012.  You can download W6ELprop at 
http://www.qsl.net/w6elprop and run several instances of the program at 
once, and flip back and forth, comparing projections for 2010 with 2011 
and 2012.  The 10 meter possibilities expand dramatically during periods 
of higher solar activity.

During the weekend the STEREO craft will surpass 97.95% coverage of the 
Sun.  You can calculate an approximation of the coverage by looking at 
http://stereo-ssc.nascom.nasa.gov/where.shtml and noting the number at 
the bottom, "Separation angle A with B." When I look at this early 
Friday morning, the number is 172.234, which corresponds to about 97.84% 
coverage.  Subtract the separation angle from 180, then divide by 360, 
subtract the result from 1 and multiply times 100.  Or skip the 
subtraction from 1 to determine the percent gap in the coverage.

To calculate the coverage at some time in the future, use the "STEREO 
Orbit Tool" at http://stereo-ssc.nascom.nasa.gov/where. Just use any 
date and time you want to test, and use the same method
described above.  At some point in early 2011 after STEREO reaches 100% 
coverage the gap will begin to grow again, but this time on the 
earth-facing side of the Sun.  The image will be filled in with data 
from the Solar Dynamics Observatory (SDO), which has a web page at 
http://www.nasa.gov/mission_pages/sdo/main. In fact, the current STEREO 
image (see http://stereo.gsfc.nasa.gov) already uses SDO data for the 
Earth-facing side of our Sun, even though that may seem redundant.  But 
this probably assures us that the transition to 100% coverage will be 
seamless.

Randy Crews, W7TJ of Spokane, Washington lives 231 miles almost directly 
east of my home in Seattle.  He's at the eastern end of Washington 
state, 15 miles from the Idaho border.  Although his
latitude is slightly lower than mine, the exact beam heading is slightly 
north of east at 89.3 degrees, instead of some fractional amount south.  
Why is this?  Because the shortest path is via the
great-circle route, and at 231 miles it is far enough to put the path 
leaving my place just slightly north of east, even though he is at 
47.6017 degrees north latitude and I am at 47.6693 degrees north
latitude.

Randy has looked over his old station logs recently, and has 
observations about the progress of Solar Cycle 24.

"Most don't realize how low we went in the Cycle 23/24 low: Previous 
cycles began with a Sunspot Number of 10-12. This cycle began with a 
Sunspot Number of about 1.5!

"Usually the cycle bottoms and picks right up within 12-13 Months from 
the low. Not the case with Cycle 24.

"This cycle has yet to see the Solar Flux above 100. By comparison, 
Cycle 22's official bottom was September of 1986, and as early as April 
of 1987, Solar Flux Values were above 100 on many days (about 6 months 
later).

"With Cycle 24 (if you measure from the low of the lows (July/August of 
2008) we are past the 2 year point, measuring from October of 2009 (when 
the number of Cycle 24 spots exceeded the old number of Cycle 23 spots) 
we are out over a year.

"I am grateful for what we have thus far. The High Bands are open (17 
meters consistently) which is a nice improvement and the higher bands 
from time to time also which is a huge step from the long dry spell in 2008.

"However, the bands have not really stepped into high gear. Flux values 
consistently above 100 (years 2004/2005) would really move us into the 
fast lane."

Thanks, Randy!

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

For more information concerning radio propagation, see the ARRL 
Technical Information Service web page at 
http://arrl.org/propagation-of-rf-signals. For an explanation of the 
numbers used in this bulletin, see 
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past 
propagation bulletins is at 
http://arrl.org/w1aw-bulletins-archive-propagation.  Find more good 
information and tutorials on propagation at 
http://mysite.ncnetwork.net/k9la/index.html.

Monthly propagation charts between four USA regions and twelve overseas 
locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL bulletins 
are at http://arrl.org/bulletins.

Sunspot numbers for December 2 through 8 were 32, 27, 48, 47, 35, 34, 
and 22, with a mean of 35. 10.7 cm flux was 86.5, 86.8, 87.4, 87.9, 
88.5, 87.1 and 87.2 with a mean of 87.3. Estimated planetary A indices 
were 3, 1, 1, 1, 2, 4 and 3 with a mean of 2.1. Estimated mid-latitude A 
indices were 1, 0, 1, 0, 3, 3 and 3 with a mean of
1.6.
NNNN
/EX