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Propagation Forecast Bulletin 15 ARLP015-24
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 12, 2024 To all radio amateurs SB PROP ARL ARLP015 ARLP015 Propagation de K7RA I did not see last Monday's eclipse, except on television. Here in the Pacific Northwest, we only got a 20% exposure, and skies were overcast. As they moved across the country displaying successive totality, I noticed the prominences on the edge of the disk. There were always between one and three little red spots at the edge. Solar activity over the past reporting week, April 4-10, remains weak. Average daily sunspot number rose from 60 to 67.9, but average solar flux declined from 136.9 to 123.2. Seven new sunspot groups emerged this week, one on April 4, three on April 5, another on April 6, one more on April 8, and another on April 10. Here is the outlook for the next few weeks, which does not seem promising. Solar flux peaks at 160 over April 17-18. Predicted solar flux is 148, 150 and 155 on April 12-14, 158 on April 15-16, 160 on April 17-18, 140 on April 19-20, 135 on April 21-22, 140 and 145 on April 23-24, 140 on April 25-26, then 135, 125 and 120 on April 27-29, and 125 on April 30 through May 10, then 130 on May 11-12, 135 on May 13-14, and 130 on May 15-18. Predicted planetary A index is quiet over the next month, starting with 5, 8, 15, 10 and 8 on April 12-16, 5 on April 17-18, 8 and 10 on April 19-20, 8 on April 21-23, 5 on April 24-27, then 8, 8 and 7 on April 28-30, 10 on May 1-3, 5 on May 4-5, 8 on May 6-8, and 5 on May 9-15, then 8 and 10 on May 16-17, and 8 on May 18-20. Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - April 11, 2024, from F.K. Janda, OK1HH: "At the end of March, it was still possible to see large sunspot groups, during the last solar rotation marked as AR3614 and especially the giant AR3615. We will see them again on the eastern limb of the solar disk this weekend. This will end a roughly two-week period of relatively quiet solar activity without major solar flares. "The Sun's total X-ray output, which has dropped by almost an order of magnitude, will increase significantly, which will have a beneficial effect on shortwave propagation. "Daily MUF values will gradually increase, while active regions will be on the eastern half of the solar disk. For that reason, here will be little probability of major geomagnetic disturbances. Of course, now that the peak of the 11-year cycle is approaching, events such as the eruption of solar plasma filaments that could affect the Earth cannot be ruled out." Douglas Barbier, N8ZVT, wrote in an email: "Why is the solar flux so low, given the number of sunspots? What else may be affecting the solar flux? "This is my first solar maximum as a ham - and at my age, might be the last. I had always heard stories of how 10m would be open 24 hours a day for voice and working all over the world with low power SSB. Sure haven't seen that yet at all." I replied: "That was nearly 70 years ago at the peak of Solar Cycle 19 when 10 meters was open 24/7. "There has never been a similar solar cycle since the dawn of radio. It was all AM back then, no SSB. "Solar flux readings come from an observatory in Penticton, BC: "https://www.spaceweather.gc.ca/forecast-prevision/solar-solaire/solarflux/sx-5-flux-en.php "I have not noticed that solar flux was low. "Because Earth is in an elliptical orbit around the Sun, a variation in distance affects solar flux. "That is why you will see adjusted values in the flux readings from Penticton. "You can get a graphic view of sunspot numbers and solar flux from the WA4TTK solar data plotting utility at: "http://www.craigcentral.com/sol.asp "You can update the data automatically using data from this weekly bulletin." Solar cycles explained: https://www.snexplores.org/article/explainer-solar-cycle A solar cycle clock: https://www.nature.com/articles/s41598-024-58960-5 Flares during eclipse: https://bit.ly/3VRBxk0 Prominences, not flares: https://bit.ly/49waWMC Solar Cycles: https://bit.ly/3PY4F5p Internet apocalypse due to solar storms: https://bit.ly/3vBW69C Dr. Tamitha Skov, WX6SWW, reports during the eclipse: https://youtu.be/Z16_Uk1vym8 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 web page 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/ . Also, check this QST article about Solar Indices: https://bit.ly/3Rc8Njt Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins . Sunspot numbers for April 4 through 10 2024 were 47, 81, 71, 79, 79, 64, and 54, with a mean of 67.9. 10.7 cm flux was 113.7, 120.5, 122.9, 124.6, 124.8, 124.4, and 131.2, with a mean of 123.2. Estimated planetary A indices were 12, 12, 10, 6, 8, 11, and 8, with a mean of 9.6. Middle latitude A index was 33, 10, 8, 5, 8, 10, and 7, with a mean of 11.6. NNNN /EX
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