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   SB PROP @ ARL $ARLP036   
   ARLP036 Propagation de K7RA   
      
   ZCZC AP36   
   QST de W1AW   
   Propagation Forecast Bulletin 36 ARLP036   
   >From Tad Cook, K7RA   
   Seattle, WA September 20, 2024   
   To all radio amateurs   
      
   SB PROP ARL ARLP036   
   ARLP036 Propagation de K7RA   
      
   Solar activity was quiet over the past week, but geomagnetic numbers were   
   way, way up.   
      
      
   Average daily sunspot numbers dropped from 178.4 to 120, and average daily   
   solar flux from 223.7 to 175.7.   
      
      
   Average daily planetary A index rocketed from 7.9 to 35.7, and middle   
   latitude numbers from 11.1 to 23.4.   
      
      
   Six new sunspot groups emerged over the past week; one each on September 13   
   and 14, two on September 16, and two each on September 17 and 18.   
      
      
   Predicted solar flux is 160 and 155 on September 20-21, 150 on September   
   22-26, then a huge leap to 230 and 225 on September 27-28, 240 on September   
   29 through October 2, 230 on October 3, 220 on October 4-5, then 215, 205 and   
   207 on October 6-8, 201, 186 and 172 on October 9-11, 173 and 175 on October   
   12-13, 170 on October 14-16, 165 on October 17-18, 170 on October 19, 225 on   
   October 20-21, then 230, 225, 230 and 225 on October 22-25, then 240 on   
   October 26-29.   
      
      
   Predicted planetary A index is 5, 10 and 8 on September 20-22, 5 on September   
   23-26, then 25, 15 and 10 on September 27-29, then 5 on September 30 through   
   October 4, 10 on October 5-6, and 5 on October 7-9, 10 on October 10, 20 on   
   October 11-13, 15 on October 14, 10 on October 15-16, then 5 on October   
   17-22, 25 on October 23-24, and 15 and 10 on October 25-26.   
      
      
   Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere -   
   September 19, 2024 from F.K. Janda, OK1HH:   
      
      
   "Overall solar activity has decreased slightly in recent days, but before   
   that AR3825 produced energetic flares, including two of the largest: X1.3 on   
   September 12th and a very strong X4.5 on September 14th. The arrival of the   
   CMEs and the onset of the disturbance, expected on the afternoon of UT Sept   
   16th, was delayed and registered as an influx of protons in the solar wind at   
   22:44 UT Sept 16th. After that, a geomagnetic disturbance started to develop,   
   which significantly affected the shortwave propagation conditions, especially   
   on 17 September.   
      
      
   "A more pronounced upsurge in solar flux can be expected once the large   
   active regions known to be present through helioseismology start to reappear   
   at the eastern limb of the solar disk. This should happen around 26   
   September. However, a repeat of the August 28-29 disturbance is expected in   
   the same period. Therefore, an improvement in propagation conditions can be   
   expected before September 26, or better yet, shortly during the onset of the   
   disturbance-after which a deterioration will occur."   
      
      
   New STCE newsletter:   
   https://www.stce.be/newsletter/newsletter.php [   
   https://www.stce.be/newsletter/newsletter.php ]   
      
      
   The latest video from Dr. Tamitha Skov, WX6SWW:   
   https://youtu.be/o0HWm0W-YRw [ https://youtu.be/o0HWm0W-YRw ]   
      
   Send your tips, reports, observations, questions and comments to   
   k7ra@arrl.net [ mailto: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 [ http://www.arrl.org/propagation ] and the   
   ARRL Technical Information Service web page at,   
   http://arrl.org/propagation-of-rf-signals [   
   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 [   
   http://arrl.org/the-sun-the-earth-the-ionosphere ] .   
      
      
   An archive of past propagation bulletins is at   
   http://arrl.org/w1aw-bulletins-archive-propagation [   
   http://arrl.org/w1aw-bulletins-archive-propagation ] .   
      
      
   More good information and tutorials on propagation are at http://k9la.us/ [   
   http://k9la.us/ ] .   
      
      
   Also, check this article:   
   https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ]   
   "Understanding Solar Indices" from September 2002 QST.   
      
   Instructions for starting or ending email subscriptions to ARRL bulletins are   
   at http://arrl.org/bulletins [ http://arrl.org/bulletins ] .   
      
      
   Sunspot numbers for September 12 through 18 2024 were 160, 127, 136, 68, 103,   
   140, and 106, with a mean of 120. 10.7 cm flux was 201.2, 185.8, 172.4,   
   172.8, 169.2, 165.4, and 163.3, with a mean of 175.7. Estimated planetary A   
   indices were 67, 37, 21, 19, 23, 71, and 12, with a mean of 35.7. Middle   
   latitude A Index was 36, 22, 22, 16, 19, 39, and 10, with a mean of 23.4.   
      
   NNNN   
   /EX   
      
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