TZUTC: -0500   
   MSGID: 402.fidonet-ls_arrl@1:2320/33 28a81308   
   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 $ARLP016   
   ARLP016 Propagation de K7RA   
      
   ZCZC AP16   
   QST de W1AW    
   Propagation Forecast Bulletin 16  ARLP016   
   From Tad Cook, K7RA   
   Seattle, WA  April 21, 2023   
   To all radio amateurs   
      
   SB PROP ARL ARLP016   
   ARLP016 Propagation de K7RA   
      
   Again this week sunspot numbers and solar flux were higher than the   
   week before.   
      
   Average daily sunspot numbers more than doubled, from 70.6 to 146.9,   
   and average daily solar flux increased from 141 to 164.5. Both   
   figures represent a substantial increase in solar activity.   
      
   Planetary A index averages went from 7.6 to 8.1, while middle   
   latitude A index advanced from 6.4 to 7.3.   
      
   Three new sunspot groups emerged on April 13, one more on April 16,   
   and another on April 17.   
      
   Predicted solar flux over the next few weeks is 145, 140 and 135 on   
   April 21-23, 130 on April 24-25, 125 on April 26-27, 160 on April   
   28-29, 165 on April 30, 172 on May 1-3, 170 on May 4, 172 on May   
   5-7, 178 on May 8, 182 on May 9-12, then 175, 178 and 170 on May   
   13-15, 168 on May 16-17, 175 on May 18, then 172 on May 19-21, then   
   168 and 162 on May 22-23, 160 on May 24-26, 165 on May 27, and 172   
   on May 28-30.   
      
   Predicted planetary A index is 20, 16, 12 and 8 on April 21-24, 5 on   
   April 25-27, 15 on April 28-30, then 12 and 10 on May 1-2, 8 on May   
   3-4, 5 on May 5-6, 12 on May 7, 5 on May 8-10, then 8 on May 11-12,   
   5 on May 13-18, then 10, 8, 5 and 5 on May 19-22, 15 and 18 on May   
   23-24, 15 on May 25-27, then 12 and 10 on May 28-29.   
      
   Weekly Commentary on the Sun, the Magnetosphere, and the Earth's   
   Ionosphere - April 20, 2023 from OK1HH.   
      
   "Of the fifteen sunspot groups observed over the past week, AR3272   
   and AR3282 were the source of most of the flares. Both had a   
   beta-gamma magnitude configuration. 61 C-class flares and 4 M-class   
   flares were observed.   
      
   "The partial halo CMEs on 15 and 16 April were the source of   
   particles that reached Earth on 18 April, when the solar wind speed   
   increased abruptly at 1308 UTC and a geomagnetic disturbance   
   developed.   
      
   "A positive phase of the ionospheric disturbance was recorded on the   
   afternoon of 18 April, followed by a negative phase on 19 April.   
   This was followed on 20 April with a significant increase in f0F2   
   and improved shortwave propagation conditions before noon UTC.   
      
   "The outlook looks promising for the first half of May, when solar   
   activity should increase further."   
      
   Dan Handa, W7WA commented on the news last week about the current   
   solar cycle reaching a peak earlier than predicted, perhaps by the   
   end of this year.   
      
   I told him I hoped it would not peak early, because I wanted to see   
   several more years of increasing activity.   
      
   Dan sent a very detailed graph of Solar Cycle 19 from 1954 to 1966,   
   and wrote: "I have read, and more than once, a slow rise means a low   
   sunspot max. The previous Solar Cycle 24 took five years to reach a   
   relatively low maximum. A rapid increase can mean a high sunspot   
   maximum. The granddaddy of our lifetime, Solar Cycle 19 peaked in   
   three years!"   
      
   I did not know this.   
      
   In a subsequent message, Dan further commented:   
      
   "There was a lot of short term variation in the Solar Cycle 19   
   sunspot number, just like we're seeing now. From the graph the   
   timing of the Solar Cycle 19 peak can be defined three different   
   ways: the daily peak, the smoothed monthly peak or the smoothed   
   yearly peak, take your pick."   
      
   Another Solar Cycle 19? Many hams have dreamed of this for the past   
   six decades.   
      
   Dale, WB6MMQ reported that the solar images in the ARRL Letter with   
   a preview of our Friday bulletin show a blank Sun. I wasn't sure   
   what he was talking about, but now I realize this must be a stock   
   image (not from me!) used in the Letter.   
      
   I sent Dale links to some recent images from Spaceweather.com:   
      
   https://www.spaceweather.com/images2023/20apr23/hmi1898.gif   
      
   https://www.spaceweather.com/images2023/19apr23/hmi1898.gif   
      
   https://www.spaceweather.com/images2023/18apr23/hmi1898.gif   
      
   https://www.spaceweather.com/images2023/17apr23/hmi1898.gif   
      
   I hope this clears up the confusion.   
      
   An odd correlation between an ancient epidemic and solar activity:   
      
   https://bit.ly/3Lsqfxf   
      
   A story about a possible early Solar peak:   
      
   https://www.space.com/sun-solar-maximum-may-arrive-early   
      
   A story about possible M-class solar flares:   
      
   https://bit.ly/3KVc1n1   
      
   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 13 through 19, 2023 were 154, 153, 151,   
   155, 162, 140, and 113, with a mean of 146.9. 10.7 cm flux was   
   159.5, 171.3, 175.8, 177.8, 166.6, 153.2, and 147, with a mean of   
   164.5. Estimated planetary A indices were 6, 7, 9, 4, 6, 13, and 12,   
   with a mean of 8.1. Middle latitude A index was 5, 10, 8, 4, 6, 9,   
   and 9, with a mean of 7.3.   
   NNNN   
   /EX   
   --- SBBSecho 3.20-Win32   
    * Origin: The Thunderbolt BBS - Little Rock, Arkansas (1:2320/33)   
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   SEEN-BY: 226/30 227/114 229/110 112 113 206 307 317 424 426 428 470   
   SEEN-BY: 229/664 700 266/512 267/800 282/1038 301/1 317/3 320/219   
   SEEN-BY: 322/757 342/200 396/45 460/58 633/267 280 281 412 418 712/133   
   SEEN-BY: 712/620 848 770/1 100 340 772/210 220 230 2320/0 33 105 304   
   SEEN-BY: 2320/401 3634/12   
   PATH: 2320/33 105 154/10 221/6 218/840 770/1 712/848 633/280 229/426