SB PROP @ ARL $ARLP016   
   ARLP016 Propagation de K7RA   
      
   ZCZC AP16   
   QST de W1AW     
   Propagation Forecast Bulletin 16  ARLP016   
   From Tad Cook, K7RA   
   Seattle, WA  April 20, 2012   
   To all radio amateurs    
      
   SB PROP ARL ARLP016   
   ARLP016 Propagation de K7RA   
      
   As promised in the ARRL Letter, this week's bulletin features a   
   report on recent solar activity and solar cycle progression from   
   Carl Leuetzelschwab, K9LA.   
      
   Solar flux and sunspot numbers reached a short term low on April   
   8-11, but now are rising again.  For the past week, April 12-18,   
   average daily sunspot numbers more than doubled compared to the   
   previous seven days, rising more than 39 points to 71.7.  Average   
   daily solar flux increased from 95.9 to 105.1.  On April 19, the day   
   following this period, the daily sunspot number rose dramatically   
   from 96 to 122, and so did solar flux values, from 121.5 to 137.8   
      
   Since April 10, eleven new sunspot groups emerged.  One each on   
   April 10-13, two on April 14, one on April 16 two on April 17 and   
   one each on April 18-19.   
      
   Predicted Solar Flux for April 20-25 is 135, followed by 130 on   
   April 26-27, 105 on April 28, 100 on April 29-30, 95 on May 1-9,   
   then rising to 100 on May 10-12 and 105 on May 13-18 and 110 on May   
   19-22.   
      
   Predicted planetary A index is 8, 5, 5, 7, 12, and 12 on April   
   20-25, 5 on April 26-29, 8 on April 30, 5 on May 1-7, and 8, 12, 15   
   and 10 on May 8-11, and 5 on May 12-20.   
      
   Alaska Dispatch ran an article with video on the solar flare   
   mentioned in K9LA's report below.  See it at   
   http://www.alaskadispatch.com/video/video-massive-eruption-suns-surface.   
      
   German ham Toni Umlandt, DD3EO mentioned another resource in   
   response to our mention in last week's bulletin ARLP015 of a public   
   remotely controlled SDR radio receiver in Walla Walla, Washington   
   that anyone can use via the internet.  He said to check   
   http://www.websdr.org/.  This lists 36 SDR receivers, and I think   
   all of them can be used simultaneously by multiple users.   
      
   K9LA's report:   
      
   Monday, April 16 gave us moderate solar activity, which was due to   
   an M1.7 X-ray flare from Region 1458 around 1745 UTC.  But since   
   then, solar activity has continued at low levels.  The daily 10.7 cm   
   solar flux is expected to slightly increase to around 120 during the   
   next several days.  There is an extremely small chance of X-Class   
   flares (1%) and a somewhat greater chance of M-Class flares (around   
   15%).   
      
   With solar activity continuing at low levels, the ascent of Cycle 24   
   noticeably slowed in the past couple months.  For example, after a   
   monthly mean 10.7 cm solar flux peak in November 2011 of 153, the   
   next three months saw ever-decreasing monthly means -- 141, 133, and   
   107 for December, January, and February, respectively.  March (last   
   month) recovered a bit with a monthly mean of 115, but April so far   
   appears to be headed for another low monthly mean (through April 18,   
   the 10.7 cm solar flux monthly mean is hovering around 102).  As a   
   side note, these up-and-downs in the monthly mean solar flux are   
   typical of a solar cycle.   
      
   But these recent low monthly means have taken their toll on the   
   smoothed 10.7 cm solar flux.  Since early 2009, the smoothed 10.7 cm   
   solar flux rose nicely.  The recent low monthly means have resulted   
   in the smoothed value pretty much leveling off in the past two   
   months at around 118.  This smoothed value is borderline for good   
   worldwide 10-Meter openings (especially East-West), so 10-Meters   
   will be at the mercy of the day-to-day variation of the F2 region.   
      
   Does this mean we've reached Cycle 24's peak?  Not necessarily --   
   other Cycles have had similar slow-downs, but then the solar   
   activity picked up again in terms of the monthly means to continue   
   the increase of the smoothed value.  The monthly means during the   
   next several months will be interesting to observe, and may give us   
   an early clue as to how high Cycle 24 will ultimately go.   
      
   Regardless of what happens with Cycle 24, the time is now to get on   
   the higher bands (especially 12-Meters and 10-Meters) to take   
   advantage of F2 region propagation.  If Cycle 24 performs to the   
   nominal prediction from the Marshall Space Flight Center   
   (http://solarscience.msfc.nasa.gov/predict.shtml), we're pretty much   
   there -- and we're not likely to have much mid latitude 50 MHz F2   
   propagation during this solar cycle (but watch for sporadic E links   
   to the equatorial ionosphere for Trans-Equatorial Propagation).  If   
   Cycle 24 performs more to the nominal prediction of the   
   International Space Environment Service   
   (http://www.swpc.noaa.gov/SolarCycle/), then we should have somewhat   
   better propagation on the higher bands in the next year or so.   
      
   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://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://myplace.frontier.com/~k9la/.   
      
   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 April 12 through 18 were 50, 50, 65, 77, 86, 78,   
   and 96, with a mean of 71.7.  10.7 cm flux was 95.3, 97.7, 98.1,   
   101.7, 107.9, 113.8 and 121.5, with a mean of 105.1.  Estimated   
   planetary A indices were 13, 19, 9, 5, 5, 8, and 8, with a mean of   
   9.6.  Estimated mid-latitude A indices were 11, 13, 7, 5, 5, 8, and   
   7, with a mean of 8.   
   NNNN   
   /EX   
      
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