SB PROP @ ARL $ARLP039 ARLP039 Propagation de K7RA ZCZC AP39 QST de W1AW Propagation Forecast Bulletin 39 ARLP039 From Tad Cook, K7RA Seattle, WA September 29, 2023 To all radio amateurs SB PROP ARL ARLP039 ARLP039 Propagation de K7RA Solar activity was up for this reporting week, September 21-27. Eight new sunspot groups appeared, two on September 21, two more on September 22, two more on September 25, another on September 26 and another on September 27. The average daily sunspot number jumped from 118.4 to 170.6, while average daily solar flux went from 149.3 to 168.8. The Autumnal Equinox was last weekend in the Northern Hemisphere, so our Earth is bathed in equal amounts of solar radiation in both hemispheres. The average daily planetary A index went from 20.4 to 17, while middle latitude numbers changed from 18.1 to 13.7. Thursday had the strongest geomagnetic activity, and Alaska's college A index was 68, triggering a geomagnetic storm with aurora visible across the northern tier of the United States. Activity peaked around 1200-1800 UTC, with planetary K index at 5.33. Regarding solar flux predictions, the next predicted peak is at 168 on October 20-23. Predicted flux values are 148 on September 29-30, then 145, 143 and 145 on October 1-3, 148 on October 4-5, 155 on October 6, 160 on October 7-8, 155 on October 9, 150 on October 10-11, 145 on October 12-14, then 150, 155, 155, 160 and 165 on October 15-19, 168 on October 20-23, then 164, 160, 160, 168 and 150 on October 24-28, then 145 and 150 on October 29-30, 155 on October 31 through November 2, 160 on November 3-4, and 155 on November 5. Predicted planetary A index is 5, 12, and 8 on September 29 through October 1, then 8, 15, 12, 8 and 15, on October 2-5, then 5 on October 6-21, then 10 and 8 on October 22-23, and 5 on October 24 through November 7, and 55 on November 8. Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - September 27, 2023 from OK1HH: "During September we saw nearly regular fluctuations in solar and geomagnetic activity. M-class flares occurred nearly every day, some accompanied by plasma eruptions (CMEs). On 24-25 September, the fourth and strongest solar-origin proton cloud (G3) of the month struck Earth. "With such a large number of disturbances, each lasting several days, there was a significant decrease in MUF and a general deterioration of shortwave propagation (September 3-5, 13-15, 18-20 and since 25 September). "After these disturbances, due to the high solar activity, relatively rapid improvements followed, the best of which was observed from 10 September onward. It culminated in a positive phase of disturbance during the daytime hours of UTC on 12 September, with the highest MUF values, and thus the best opening of the upper shortwave bands. This also made the following deterioration, which started already on the night of 13 September, even more noticeable. "Given the number and duration of disturbances and despite several improvements, overall propagation was below average. This pattern began in August and given the trend in solar activity, looks set to continue for the time being." Gregory Andracke, W2BEE sent these two articles about Aurora Borealis: https://nbcnews.to/3PUVH9q https://bbc.in/3PQLhrj Check out his web site: http://www.andracke.com/ Here are more articles and videos about aurora: https://bit.ly/3PEnsl4 https://bit.ly/3PU22Sy https://bit.ly/48ASMtK https://bit.ly/46w7CzQ https://bit.ly/3PXAGuX https://bit.ly/48A6Kfk https://bit.ly/3PBgE7V https://bit.ly/3PzOJFw https://bit.ly/469xDFw https://bit.ly/3rvgRBA 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. 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 article from September, 2002 QST: https://bit.ly/3Rc8Njt Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins . Sunspot numbers for September 21 through 27, 2023 were 159, 184, 198, 172, 164, 179, and 138, with a mean of 170.6. 10.7 cm flux was 168.1, 175.7, 173, 173.7, 170.2, 164.9, and 156, with a mean of 168.8. Estimated planetary A indices were 10, 8, 10, 21, 23, 32, and 15, with a mean of 17. Middle latitude A index was 10, 7, 9, 17, 15, 26, and 12, with a mean of 13.7. NNNN /EX