SB PROP @ ARL $ARLP014<br />ARLP014 Propagation de K7RA<br /><br />ZCZC AP14<br />QST de W1AW <br />Propagation Forecast Bulletin 14 ARLP014<br />>From Tad Cook, K7RA<br />Seattle, WA April 7, 2006<br />To all radio amateurs <br /><br />SB PROP ARL ARLP014<br />ARLP014 Propagation de K7RA<br /><br />Some renewed activity this week with the appearance of a crowd of<br />sunspots, 865, 866, 867, 868 and 869. On March 25-27 there were 0<br />sunspots, then these new spots appeared on March 28, 29, April 2, 5<br />and 6. The big one, sunspot 865, is about to rotate out of view.<br /><br />The daily sunspot number reached a peak of 105 on April 6. To find a<br />daily sunspot number this high, one must look back to last summer,<br />when the sunspot number on August 2 was 112, over seven months ago.<br />But this is just another one of those little up-ticks as this solar<br />cycle gradually declines, probably reaching a minimum in less than a<br />year.<br /><br />You can see the projection for the next year and a half in the<br />current April 4 issue of the NOAA Preliminary Report and Forecast of<br />Geophysical Data, in PDF format. Look on page 9 of this issue at,<br />
http://www.sec.noaa.gov/weekly/pdf/prf1596.pdf. You'll see that the<br />predicted smoothed sunspot number for April 2006 is 12, and that<br />this chart predicts a decline that won't rise again to the current<br />level until some time around August or September 2007. But after<br />that, the next solar cycle (based on past cycle behavior) should<br />rise faster than the current one declined.<br /><br />With the first quarter of the calendar year ended, we should examine<br />the decline of quarterly averages for daily sunspot numbers. Three<br />months gives us slightly less than three and a third rotations of<br />the sun, and is enough time to smooth out daily or weekly variations<br />so we can see a more general trend.<br /><br />>From the first quarter of 2003 through the first quarter of 2006,<br />the average daily sunspot number was 120.3, 107.3, 110.2, 99.2,<br />72.9, 71.3, 69.3, 61, 46.1, 55.7, 58, 36 and 18.1.<br /><br />The average daily solar flux for the same period was 134.3, 124.2,<br />120.8, 137.4, 111.1, 99.5, 111, 104.8, 96.4, 93.1, 93.6, 84.5 and<br />78.5.<br /><br />I think you'll agree the general trend is down. An average daily<br />sunspot number of 18.1 for the first quarter of the year can be<br />easily compared to the minimum between cycles 22 and 23. From the<br />fourth quarter of 1995 to the second quarter of 1997, the average<br />daily sunspot numbers for each quarter were 21.3, 13.1, 13, 12.4,<br />14.2, 11.3 and 25.4. You can see that our recent quarterly average<br />of 18.1 fits right in toward the bottom of the last cycle.<br /><br />For the near term, expect sunspot numbers and solar flux to decline<br />gradually. Over the next week, U.S. Air Force Space Weather<br />Operations predict a planetary A index for April 7-13 of 10, 8, 20,<br />15, 12, 7 and 5. Over those same days they show a decline of solar<br />flux values from 100 to 80. Geophysical Institute Prague shows quiet<br />to unsettled conditions for April 7, April 8 with quiet conditions,<br />unsettled conditions on April 9, active conditions April 10,<br />unsettled to active on April 11, April 12 unsettled, and quiet to<br />unsettled on April 13. So Prague thinks the peak in geomagnetic<br />instability should occur around April 10, but US Air Force predicts<br />April 9.<br /><br />Michael Shelly, WB2KKI of Pocono Summit, Pennsylvania wrote in to<br />ask about MUF charts. These used to appear in QST, and they showed<br />the predicted change in Maximum Usable Frequency over a variety of<br />paths (for instance, West Coast USA to Japan) for a typical 24 hour<br />period, based on the month, and the predicted smoothed sunspot<br />number for the period.<br /><br />These moved to the web some time ago, and you can find links to them<br />on the ARRL web site at
http://www.arrl.org/qst/propcharts/. Note<br />that this page also has a link to QST articles by Jerry Hall, K1TD,<br />on how to use this tool.<br /><br />We get mail asking us for more useful information about predicted<br />propagation. For instance, when is a good time to work Europe, and<br />on what band? This is a good general question, but the readers of<br />this bulletin are all over the world, so it is difficult to make<br />these generalizations. It is even difficult to make good general<br />statements if we just limit our area of interest to North America,<br />because it covers such a large area. What is true for the southern<br />part of the East Coast may not be true for the north, or Midwest, or<br />either end of the West Coast.<br /><br />But given data from public sources, you can get some good general<br />custom projections of propagation from your location to most other<br />locations on just about any HF band.<br /><br />First, get some propagation prediction software. A great one is<br />ACE-HF Pro, which you can find at
http://www.acehf.com. If you want<br />to try a piece of free software, the one we've mentioned numerous<br />times in the past is W6ELprop, which you can download at<br />
http://www.qsl.net/w6elprop/. This program works with either solar<br />flux or sunspot numbers, but your best bet is probably to use the<br />average sunspot number for the past few days, rather than the latest<br />number. You can find them listed at,<br />
http://www.sec.noaa.gov/ftpdir/indices/DSD.txt.<br /><br />So if I were doing one now, the latest available data is through<br />April 6. So I would take the average by adding 100, 99 and 99, and<br />dividing by 3, which gives us 99.3. If you want to enter the K index<br />into the program, you can get the mid-latitude values from WWV<br />either off the air at 18 minutes after the hour, or over the web at,<br />
http://sec.noaa.gov/ftpdir/latest/wwv.txt. You can also look at<br />recent geomagnetic activity at,<br />
http://www.sec.noaa.gov/ftpdir/indices/DGD.txt.<br /><br />And last, we depend on the National Oceanic and Atmospheric<br />Administration's Space Weather Service for our main source of data.<br />Funding for these services in the administration's 2007 budget was<br />expected to stay at the current level, but now it looks like severe<br />cuts may be coming. I put up some information about this on the web<br />at,
http://tinyurl.com/nbnc7.<br /><br />If you would like to make a comment or have a tip for our readers,<br />email the author at, []k7ra@arrl.net.[/]<br /><br />For more information concerning radio propagation and an explanation<br />of the numbers used in this bulletin see the ARRL Technical<br />Information Service propagation page at,<br />
http://www.arrl.org/tis/info/propagation.html. An archive of past<br />propagation bulletins is found at,
http://www.arrl.org/w1aw/prop/.<br /><br />Sunspot numbers for March 30 through April 5 were 35, 39, 39, 68,<br />79, 62 and 88 with a mean of 58.6. 10.7 cm flux was 83.9, 86.3, 87,<br />91.1, 100.4, 99.5, and 99, with a mean of 92.5. Estimated planetary<br />A indices were 4, 4, 2, 1, 1, 7 and 29 with a mean of 6.9. Estimated<br />mid-latitude A indices were 2, 2, 1, 1, 1, 4 and 18, with a mean of<br />4.1.<br />NNNN<br />/EX
