[South Florida DX Association] ARLP051 Propagation de K7RA

[Bill Marx]

SB PROP ARL ARLP051
> ARLP051 Propagation de K7RA
> 
> The past couple of days have seen robust solar activity, with flares
> and strong solar wind. On Wednesday and Thursday, December 6 and 7,
> the planetary A index rose to 28, then 25. On December 5 a large X9
> class solar flare emerged from the sun's eastern side, but it wasn't
> earth directed. This was from a large sunspot 930, which drove the
> sunspot number to 59 on the same day as the solar flare, the same
> level as five days earlier. Wednesday, December 6 saw a smaller X6
> flare, and currently early Friday morning we are seeing a strong
> solar wind, with the interplanetary magnetic field pointing south,
> making us vulnerable. There is a chance of more flares, which might
> be bad news for the ARRL 10 Meter Contest this weekend.
> 
> Flare activity caused a 10.7 cm solar flux reading at Penticton,
> British Columbia to jump off the scale. The noon reading showed a
> solar flux of 573.4, and had to be adjusted downward to 103 for the
> day.
> 
> Currently a forecast from NOAA and the U.S. Air Force calls for a
> planetary A index on December 8-12 of 30, 50, 40, 20 and 10.  The
> predicted A index of 50 and 40 for December 9-10 does not bode well
> for the weekend contest. Even if the geomagnetic activity is this
> strong, there still should be some north-south trans-equatorial
> propagation on 10 meters. But here we see an average sunspot number
> of 52 for this week, 35 points higher than last week, and of course
> the downside is greater chance for solar flares.
> 
> There is a new prediction for the sunspot cycle minimum. Until
> recently, the minimum was predicted to have a smoothed sunspot
> number of 6 centered on March and April 2007. The new forecast moves
> the minimum out a little further and not as low, with a smoothed
> sunspot number of 7 for May 2007. You can see the difference in the
> table on page 11 of the SEC Preliminary Report and Forecast for this
> week, compared with the issue from four weeks ago.  The old forecast
> is at, http://www.sec.noaa.gov/weekly/pdf/prf1627.pdf on page 11,
> and the new one at, http://www.sec.noaa.gov/weekly/pdf/prf1631.pdf ,
> also on page 11. This later and higher minimum makes sense, because
> we haven't seen weeks in a row of 0 sunspot days.
> 
> Last week's Propagation Forecast Bulletin ARLP050 mentioned a theory
> about cooling in the upper ionosphere causing greater density in
> lower layers. It turns out that data from different locations shows
> different results, and the net effect doesn't look strong or
> conclusive. If you do a web search for terms such as "long term
> ionosphere change" you'll find abstracts for several scientific
> papers on the subject. The most interesting thing I ran across
> (thanks to K9LA) was the map on page 12 of the PDF at,
> http://tinyurl.com/yyn4ut. The hmF2 referred to in this document is
> the height of the densest portion of the F2 layer, with positive
> trends at some ionosonde stations and negative at others. The trend
> for change in height of the F2 layer is also very slight. It comes
> out to about two and a half miles per decade, or
> .41 km per year, for ionosonde stations that show any effect.
> 
> Jon Jones, N0JK commented that recently in the CQ Worldwide CW
> Contest even with solar activity so low, HC8N on 10 meters worked
> 1,838 stations in 32 zones and 113 countries. Also, Dave Deatrick,
> WA8OLD way up in Northern Michigan next to Sault Ste Marie, Ontario,
> remarks that he's had great luck recently on 40 meters with a
> shortened dipole at 28 feet and 100 watts. He worked 5A7A, CN2R and
> several European stations. He is surprised at what he can work on 40
> meters with a simple antenna and low power.
> 
> If you would like to make a comment or have a tip for our readers,
> email the author at, k7ra at 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 November 30 through December 6 were 59, 58, 55,
> 46, 43, 59 and 44 with a mean of 52. 10.7 cm flux was 84.1, 84.2,
> 87.3, 86.5, 92.8, 102.4, and 103, with a mean of 91.5. Estimated
> planetary A indices were 28, 4, 2, 3, 1, 2 and 28 with a mean of
> 9.7. Estimated mid-latitude A indices were 15, 3, 1, 2, 1, 2 and 15,
> with a mean of 5.6.
> NNNN
> /EX
> 
> 
>