[South Florida DX Association] ARLP014 Propagation de K7RA

[Bill Marx]

SB PROP ARL ARLP014
> ARLP014 Propagation de K7RA
> 
> Some renewed activity this week with the appearance of a crowd of
> sunspots, 865, 866, 867, 868 and 869. On March 25-27 there were 0
> sunspots, then these new spots appeared on March 28, 29, April 2, 5
> and 6. The big one, sunspot 865, is about to rotate out of view.
> 
> The daily sunspot number reached a peak of 105 on April 6. To find a
> daily sunspot number this high, one must look back to last summer,
> when the sunspot number on August 2 was 112, over seven months ago.
> But this is just another one of those little up-ticks as this solar
> cycle gradually declines, probably reaching a minimum in less than a
> year.
> 
> You can see the projection for the next year and a half in the
> current April 4 issue of the NOAA Preliminary Report and Forecast of
> Geophysical Data, in PDF format. Look on page 9 of this issue at,
> http://www.sec.noaa.gov/weekly/pdf/prf1596.pdf. You'll see that the
> predicted smoothed sunspot number for April 2006 is 12, and that
> this chart predicts a decline that won't rise again to the current
> level until some time around August or September 2007. But after
> that, the next solar cycle (based on past cycle behavior) should
> rise faster than the current one declined.
> 
> With the first quarter of the calendar year ended, we should examine
> the decline of quarterly averages for daily sunspot numbers. Three
> months gives us slightly less than three and a third rotations of
> the sun, and is enough time to smooth out daily or weekly variations
> so we can see a more general trend.
> 
> From the first quarter of 2003 through the first quarter of 2006,
> the average daily sunspot number was 120.3, 107.3, 110.2, 99.2,
> 72.9, 71.3, 69.3, 61, 46.1, 55.7, 58, 36 and 18.1.
> 
> The average daily solar flux for the same period was 134.3, 124.2,
> 120.8, 137.4, 111.1, 99.5, 111, 104.8, 96.4, 93.1, 93.6, 84.5 and
> 78.5.
> 
> I think you'll agree the general trend is down. An average daily
> sunspot number of 18.1 for the first quarter of the year can be
> easily compared to the minimum between cycles 22 and 23. From the
> fourth quarter of 1995 to the second quarter of 1997, the average
> daily sunspot numbers for each quarter were 21.3, 13.1, 13, 12.4,
> 14.2, 11.3 and 25.4. You can see that our recent quarterly average
> of 18.1 fits right in toward the bottom of the last cycle.
> 
> For the near term, expect sunspot numbers and solar flux to decline
> gradually. Over the next week, U.S. Air Force Space Weather
> Operations predict a planetary A index for April 7-13 of 10, 8, 20,
> 15, 12, 7 and 5. Over those same days they show a decline of solar
> flux values from 100 to 80. Geophysical Institute Prague shows quiet
> to unsettled conditions for April 7, April 8 with quiet conditions,
> unsettled conditions on April 9, active conditions April 10,
> unsettled to active on April 11, April 12 unsettled, and quiet to
> unsettled on April 13. So Prague thinks the peak in geomagnetic
> instability should occur around April 10, but US Air Force predicts
> April 9.
> 
> Michael Shelly, WB2KKI of Pocono Summit, Pennsylvania wrote in to
> ask about MUF charts. These used to appear in QST, and they showed
> the predicted change in Maximum Usable Frequency over a variety of
> paths (for instance, West Coast USA to Japan) for a typical 24 hour
> period, based on the month, and the predicted smoothed sunspot
> number for the period.
> 
> These moved to the web some time ago, and you can find links to them
> on the ARRL web site at http://www.arrl.org/qst/propcharts/. Note
> that this page also has a link to QST articles by Jerry Hall, K1TD,
> on how to use this tool.
> 
> We get mail asking us for more useful information about predicted
> propagation. For instance, when is a good time to work Europe, and
> on what band? This is a good general question, but the readers of
> this bulletin are all over the world, so it is difficult to make
> these generalizations. It is even difficult to make good general
> statements if we just limit our area of interest to North America,
> because it covers such a large area. What is true for the southern
> part of the East Coast may not be true for the north, or Midwest, or
> either end of the West Coast.
> 
> But given data from public sources, you can get some good general
> custom projections of propagation from your location to most other
> locations on just about any HF band.
> 
> First, get some propagation prediction software. A great one is
> ACE-HF Pro, which you can find at http://www.acehf.com. If you want
> to try a piece of free software, the one we've mentioned numerous
> times in the past is W6ELprop, which you can download at
> http://www.qsl.net/w6elprop/. This program works with either solar
> flux or sunspot numbers, but your best bet is probably to use the
> average sunspot number for the past few days, rather than the latest
> number. You can find them listed at,
> http://www.sec.noaa.gov/ftpdir/indices/DSD.txt.
> 
> So if I were doing one now, the latest available data is through
> April 6. So I would take the average by adding 100, 99 and 99, and
> dividing by 3, which gives us 99.3. If you want to enter the K index
> into the program, you can get the mid-latitude values from WWV
> either off the air at 18 minutes after the hour, or over the web at,
> http://sec.noaa.gov/ftpdir/latest/wwv.txt. You can also look at
> recent geomagnetic activity at,
> http://www.sec.noaa.gov/ftpdir/indices/DGD.txt.
> 
> And last, we depend on the National Oceanic and Atmospheric
> Administration's Space Weather Service for our main source of data.
> Funding for these services in the administration's 2007 budget was
> expected to stay at the current level, but now it looks like severe
> cuts may be coming. I put up some information about this on the web
> at, http://tinyurl.com/nbnc7.
> 
> 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 and an explanation
> of the numbers used in this bulletin see the ARRL Technical
> Information Service propagation page at,
> http://www.arrl.org/tis/info/propagation.html. An archive of past
> propagation bulletins is found at, http://www.arrl.org/w1aw/prop/.
> 
> Sunspot numbers for March 30 through April 5 were 35, 39, 39, 68,
> 79, 62 and 88 with a mean of 58.6. 10.7 cm flux was 83.9, 86.3, 87,
> 91.1, 100.4, 99.5, and 99, with a mean of 92.5. Estimated planetary
> A indices were 4, 4, 2, 1, 1, 7 and 29 with a mean of 6.9. Estimated
> mid-latitude A indices were 2, 2, 1, 1, 1, 4 and 18, with a mean of
> 4.1.
> NNNN
> /EX
> 
>