SB PROP @ ARL $ARLP015   
   ARLP015 Propagation de K7RA   
      
   ZCZC AP15   
   QST de W1AW     
   Propagation Forecast Bulletin 15  ARLP015   
   From Tad Cook, K7RA   
   Seattle, WA  April 15, 2011   
   To all radio amateurs    
      
   SB PROP ARL ARLP015   
   ARLP015 Propagation de K7RA   
      
   The daily sunspot number reached a new high for Solar Cycle 24 on   
   Wednesday, April 13, 2011, when it hit 153. I looked back over this   
   calendar year, and saw that the previous high was 137 on March 8,   
   2011, 16 points lower than Wednesday.  That week was reported in our   
   Propagation Forecast Bulletin ARLP010 (see http://snurl.com/27snys),   
   which said, "The last time the daily sunspot number was higher than   
   this was July 7, 2005, when it was 149."   
      
   I knew I would have to inspect sunspot numbers prior to that date to   
   find something higher, which would be on the after-the-peak   
   down-side of Solar Cycle 23. I went to the   
   http://www.swpc.noaa.gov/ftpdir/indices/old_indices/2005_DSD.txt   
   link and only had to look two days earlier to July 5, 2005, when it   
   was 181. In fact, the day prior to that was even higher, 192.  If   
   you look at that table, you can see that around the end of June and   
   early July 2005 the Sun produced a good burst of activity on Cycle   
   23's down side. You can read a bulletin from early July 2005 at   
   http://snurl.com/27snzj.   
      
   Apparently at that time we must have assumed that we were already   
   near a low point in the sunspot cycle, but did not know that five   
   years later we would still be waiting for a significant increase in   
   sunspot activity. The bulletin mentions this was the most activity   
   seen since November 26, 2003.   
      
   The average sunspot number for the past week rose 21.6 points, from   
   68.3 to 89.9.  Average daily solar flux declined though, by 2.6   
   points to 109.2.   
      
   Eight new sunspot groups emerged this week.  There was one new group   
   on April 7, two more on April 8, another new one on April 11, two   
   more on April 12, and another new group on Wednesday, April 13, and   
   yet another on April 14.   
      
   Predicted solar flux values from NOAA/USAF for the near term have   
   increased since the forecast in the ARRL Letter on Thursday.   
   Predicted solar flux is 125 and 128 on April 15-16, 130 on April   
   17-19, and 135 on April 20-21 and 115 on April 22-23.  Planetary A   
   index for the same period is predicted to be 5 on April 15-17, 7 and   
   10 on April 18-19, and 5 on April 20-27. Geophysical Institute   
   Prague predicts quiet geomagnetic conditions April 15-17, quiet to   
   unsettled April 18, active conditions April 19, and unsettled   
   conditions April 20-21.   
      
   On April 12 a solar wind stream hit Earth, causing aurora to be   
   visible across the northern tier states in the U.S.  The high   
   latitude College A index hit 39, and planetary A index was 23. The   
   next period of higher geomagnetic activity predicted by NOAA/USAF is   
   April 28-29, with a planetary A index of 12 and 15.   
      
   Jon Jones, N0JK of Wichita, Kansas reports, "I heard OA4TT (Peru) on   
   50.135 MHz on April 4 at 2020z. KN5O in LA had OA4TT in strong, was   
   weak for me.  Perhaps direct F2 to the Gulf Coast then weak Es on to   
   KS. KN5O is on my great circle bearing to Peru."   
      
   Jeff Hartley, N8II of Shepherdstown, West Virginia reports, "There   
   have been plenty of recent propagation surprises. Last Friday, April   
   8, K3SWZ near Harrisburg, PA reported to me working DU9RG on 10   
   meter SSB at 2348z. Sunset here was 2343Z. I didn't find Robin, but   
   did work first VK6 of Cycle 24 on 10 meters, VK6DU on SSB around   
   2350z. There were several other eastern VKs and ZLs with good   
   signals on 10 around the same time.   
      
   "I have worked 5N7M around 2300z on 10 CW and he is frequently on 10   
   and 12 meters very late for him right around the bottom of the band.   
   I heard him as late as 0044z with a good signal on 12 meters last   
   night, then he went down to the bottom of 15 CW around 0100z. 5M2TT   
   (Liberia) was running a big pile-up on 17 meters SSB around 0000z   
   and was worked on Monday around 2330z on both 10 meters phone and   
   CW. 15 has been regularly open to JA in our evenings this week and   
   was still open at 0110z last night. Earlier in the week I had a   
   'run' of JAs on 15 CW around 2330z with signals up to S9, not an   
   every day event for this QTH with about the poorest prop to JA in   
   the USA (beam heading is 330)."   
      
   To Japan, Jeff is over 6,800 miles. From K7RA in Seattle it is about   
   4,900 miles at 300 degrees.   
      
   Dick Grubb, W0QM of Boulder, Colorado suggested that in addition to   
   the STEREO web site at http://stereo.gsfc.nasa.gov/, another view is   
   at http://snurl.com/27so8j.  This image shows the same data that are   
   displayed at the first site, but flattened out instead of the   
   spinning globe.   
      
   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 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 April 7 through 13 were 73, 97, 56, 56, 80, 114,   
   and 153, with a mean of 89.9. 10.7 cm flux was 112.3, 108.7, 105,   
   104.8, 105.8, 110.3, and 117.8, with a mean of 109.2. Estimated   
   planetary A indices were 6, 8, 10, 5, 9, 23, and 14, with a mean of   
   10.7. Estimated mid-latitude A indices were 4, 5, 4, 3, 5, 14, and   
   10, with a mean of 6.4.   
   NNNN   
   /EX   
      
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