TZUTC: -0500   
   MSGID: 418.fidonet-ls_arrl@1:2320/33 28b13d6d   
   PID: Synchronet 3.20a-Win32 master/a59d7d36d Apr 13 2023 MSC 1929   
   TID: SBBSecho 3.20-Win32 master/a59d7d36d Apr 13 2023 MSC 1929   
   BBSID: TBOLT   
   CHRS: ASCII 1   
      
   SB PROP @ ARL $ARLP017   
   ARLP017 Propagation de K7RA   
      
   ZCZC AP17   
   QST de W1AW    
   Propagation Forecast Bulletin 17  ARLP017   
   From Tad Cook, K7RA   
   Seattle, WA  April 28, 2023   
   To all radio amateurs   
      
   SB PROP ARL ARLP017   
   ARLP017 Propagation de K7RA   
      
   At 0134 UTC on April 27, The Australian Space Weather Forecasting   
   Centre issued a geomagnetic disturbance warning:   
      
   "An equatorial coronal hole is currently elevating solar wind   
   speeds. Combined with the anticipated impact from a recent CME on   
   April 27, geomagnetic activity is expected to be at G0-G1 levels   
   over April 27-28, with a slight chance of an isolated period of G2."   
      
   Solar and geomagnetic indicators moved in opposite directions this   
   week. Average daily sunspot numbers over April 20-26 made a dramatic   
   drop from 146.9 to 91.4, and average daily solar flux from 164.5 to   
   139.4.   
      
   Average daily planetary A index more than tripled from 8.1 to 26.9,   
   while average middle latitude A index more than doubled from 7.3 to   
   15.6.   
      
   Solar wind and explosions caused all this grief.   
      
   Spaceweather.com reported that on April 21, a large magnetic   
   filament on the Sun exploded, hurling debris toward Earth.   
      
   Later they reported that on April 23 at 1737 UTC a CME hit Earth,   
   sparking a severe G4-class geomagnetic storm. Aurora was visible as   
   far south as southern New Mexico and Texas.   
      
   The planetary K index went as high as 8 over April 23-24.   
      
   Predicted solar flux over the next month is 135 on April 28-30, 140   
   on May 1-2, 135 on May 3-4, 140 on May 5-6, then  145, 150, 155, 160   
   and 165 on May 7-11, 170 on May 12-13, then 165, 160, 155, 150, 145   
   and 140 on May 14-19, 135 on May 20-21, 130 and 125 on May 22-23,   
   120 on May 24-25, then 125, 130 and 135 on May 26-28, 140 on May 29   
   through June 2, then 145, 150, 155, 160, and 165 on June 3-7.   
      
   Predicted planetary A index is 25, 16 and 12 on April 28-30, 8 on   
   May 1-5, 12 and 10 on May 6-7, 8 on May 8-9, then 5, 5 and 12 on May   
   10-12, 5 on May 13-15, 8 on May 16-17, 5 on May 18-22, then 15 and   
   18 on May 23-34, and 15 on May 25-27, then 12 and 10 on May 28-29, 8   
   on May 30-31, then 5, 5 and 12 on June 1-3, and 5 on June 4-6.   
      
   Weekly Commentary on the Sun, the Magnetosphere, and the Earth's   
   Ionosphere - April 27, 2023 from F.K. Janda, OK1HH.   
      
   "The most important event of the last seven days was the solar flare   
   on 21 April with a maximum at 1812 UTC (1744 - 1857 UT). It was a   
   long duration event (LDE), accompanied by the ejection of a cloud of   
   coronal plasma into space, at a location on the Sun where there is a   
   high probability of the cloud hitting the Earth. It is therefore not   
   surprising that all forecast centres agreed in predicting the   
   impending disturbance.   
      
   "The speed of the solar wind jumped up on 23 April at 1703 UTC,   
   after which a geomagnetic disturbance began to develop. It was much   
   stronger than expected (max K=8 and G4 instead of the expected K=6   
   and G1-2). Auroras were observed with two maxima - in Europe on 23   
   April mainly between 1900-2100 UTC and in North America on 24 April   
   between 0300-0400 UTC.   
      
   "Thereafter, propagation conditions deteriorated significantly,   
   especially on 24-25 April, with one interesting variation of the   
   evolution: the calming of the geomagnetic field on the morning of 25   
   April UTC was followed by a further development of the disturbance   
   with an albeit shorter but significant improvement. The return of   
   the critical frequencies of the F2 layer and the improvement of   
   shortwave propagation conditions toward the mean continued only   
   slowly in the following days, as intervals of increased geomagnetic   
   activity occurred daily. The lowest f0F2 were observed on the night   
   of 23-24 April. The following night was slightly better."   
      
   Rocky Riggs, W6RJK in Truckee, California wrote:   
      
   "I was not very active until recently when I was introduced to POTA.   
   The park I frequent the most would typically give me 40-60 contacts   
   in a 2 hour period.   
      
   "On Monday, the 24th, I went to the same park, and in 30+ minutes   
   had no contacts and couldn't hear anyone either. I later found out   
   that the solar storm was causing most of our radio problems. Until   
   then, I had never considered much about solar flares, or how the Sun   
   influences radio propagation. Now, finally, I'm trying to learn as   
   much as I can. The K7RA Solar Update in the ARRL Newsletter is   
   FANTASTIC, and will be my source going forward to help me learn and   
   understand.   
      
   "Here's my question.  Is there a 'real time' place where I can go to   
   determine if a particular band has good propagation (I typically use   
   20m and 40m)?   
      
   "You know, like before I go out and get all set up and it's a 'goose   
   egg.'"   
      
   I replied:   
      
   "I recommend pskreporter.info, and look on the map screen for FT8   
   signals from your grid square and where they are heard. You don't   
   have to use FT8 to use this.   
      
   "You can also check for the 'country of callsign' option with your   
   own or any callsign.  When I do this for 10 meters, this week it has   
   been showing no propagation from my area, but lots of 10 meter   
   propagation in the south and across the east coast.   
      
   "I use FT8 a lot to study propagation."   
      
   Angel Santana, WP3GW in Trujillo Alto, Puerto Rico wrote:   
      
   "Been doing a lot of FT8 these months. More DXpeditions are   
   including its operation.  Just last week on April 16th at 1939 UTC   
   worked VU7W and in WARD April 18th T30UN at 0721 on 40m and 0735 on   
   30m, the two ATNOs."   
      
   (I think WARD refers to World Amateur Radio Day, and of course ATNO   
   refers to All Time New One, something I did not know until a few   
   years ago. -K7RA)   
      
   "But on the 20th, at 0800 UTC, saw stations on 10 meters, normally   
   you do not hear them on any mode at that time. Then I began to call   
   them and a few from Europe contacted me. Then at about 0845 UTC,   
   'poof' they disappeared.   
      
   "These are the things that make me say that it is because of the   
   'crazy prop' (la propa loca)."   
      
   Tomas Hood, NW7US has a monthly propagation column in CQ Magazine,   
   which is a great resource. In the March issue he writes about the   
   promising progress of Solar Cycle 25.   
      
   Another great resource is Chapter 19, the "Propagation of Radio   
   Signals" in the 2023 100th edition of the ARRL Handbook. It contains   
   the most comprehensive treatment of radio propagation I have ever   
   seen and goes on for 38 pages.   
      
   Aurora observed in China:   
      
   https://bit.ly/41KyY3w   
      
   Aurora in Iowa:   
      
   https://bit.ly/3Nlvy2S   
      
   An article explaining aurora:   
      
   https://bit.ly/3n7ROm2   
      
   A Science & Tech article about Sun science:   
      
   https://bit.ly/429Sqq9   
      
   From 2017, a NASA sunspot video:   
      
   https://www.exploratorium.edu/video/nasa-life-sunspot   
      
   Send your tips, reports, observations, questions and comments to   
   k7ra@arrl.net. When reporting observations, don't forget to   
   tell us which mode you were operating.   
      
   For more information concerning shortwave radio propagation, see   
   http://www.arrl.org/propagation and the ARRL Technical Information   
   Service at http://arrl.org/propagation-of-rf-signals . For an   
   explanation of 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 . More good   
   information and tutorials on propagation are at http://k9la.us/ .   
      
   Instructions for starting or ending email distribution of ARRL   
   bulletins are at http://arrl.org/bulletins .   
      
   Sunspot numbers for April 20 through 26, 2023 were 97, 114, 87, 86,   
   88, 87, and 81, with a mean of 91.4. 10.7 cm flux was 147, 151.2,   
   141.2, 135.2, 133.9, 130.7, and 136.5, with a mean of 139.4.   
   Estimated planetary A indices were 5, 9, 7, 66, 76, 10, and 15, with   
   a mean of 26.9. Middle latitude A index was 5, 8, 6, 32, 39, 7, and   
   12, with a mean of 15.6.   
   NNNN   
   /EX   
   --- SBBSecho 3.20-Win32   
    * Origin: The Thunderbolt BBS - Little Rock, Arkansas (1:2320/33)   
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