SB PROP @ ARL $ARLP032 ARLP032 Propagation de K7RA ZCZC AP32 QST de W1AW Propagation Forecast Bulletin 32 ARLP032 From Tad Cook, K7RA Seattle, WA August 23, 2024 To all radio amateurs SB PROP ARL ARLP032 ARLP032 Propagation de K7RA Ten new sunspot groups appeared over this reporting week (August 15-21), but both solar flux and sunspot numbers were lower, due to the extraordinary numbers in the previous week. Average daily sunspot number declined from 255 to 180.3, while average daily solar flux went from 284.9 to 232.7. Geomagnetic numbers were quieter. Average daily planetary A index declined from 28.6 to 11.9, and average daily middle latitude numbers sank from 17.8 to 12. On August 17 the planetary A index was 31, caused by a CME around 1400 UTC. A strong G3 geomagnetic storm was the result. One new sunspot group appeared on August 15, and two more emerged on every day from August 16 to 19, and one more on August 21. Predicted solar flux is 230 and 235 on August 23-24, then 240 on August 25-26, 230 on August 27, 235 on August 28-29, 205, 210 and 215 on August 30 through September 1, 220 on September 2-3, 225 on September 4-6, 220 on September 7, 225 on September 9, 230 on September 10-12, and 225 on September 13-16, 215 and 210 on September 17-18, 200 on September 19-20, then 205, 210, 205 and 200 on September 21-24, and 205 on September 25-26. The planetary A index prediction shows 8 on August 23, and 5 on August 24 to September 17, 18 and 12 on September 18-19, then 5 on September 20 through the first week in October. I get mail asking why ten meters isn't open during all of the recent high solar activity. The reason is the season. We have to be much closer to the autumnal equinox to see ten meters open regularly. Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere for August 22, 2024 from OK1HH. "After the solar flare X1.1 on 14 August, accompanied by a CME, we expected a geomagnetic storm. A more accurate prediction was provided by the NASA model - the disturbance in agreement with it started on 17 August around 1400 UT. The geomagnetic storm was strong (G3), probably triggered by the arrival of more than one CME. We observe two to three sunspot groups on the solar disk that can produce moderate flares (they have a 'beta-gamma' magnetic field). There are usually 10 - 12 groups in total. Coronal holes are few and relatively small, which reduces the likelihood of an increase in solar wind speed. Semi-regularly, days with higher MUF values (until Aug 17, Aug 19 and Aug 21) alternated with decreases (Aug 14, Aug 18, Aug 20...), which could only be predicted to a very limited extent and only for shorter intervals based on measured interplanetary magnetic field variations. But these are mostly impossible to predict." Solar activity has remained at a 20-year high for most of this summer, and so far there is no indication of a possible decline. 20 year record: https://bit.ly/3ACRphS Kepler. Thanks to David Moore for this: https://cnn.it/3Xff40v 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. Understanding Solar Indices from September 2002 QST: https://bit.ly/3Rc8Njt. Instructions for starting or ending email subscriptions to ARRL bulletins are at http://arrl.org/bulletins. Sunspot numbers for August 15 through 21 2024 were 164, 169, 170, 170, 213, 200, and 176, with a mean of 180.3. 10.7 cm flux was 227.4, 224.9, 229.5, 231, 239.1, 238.2, and 239, with a mean of 232.7. Estimated planetary A indices were 6, 8, 31, 13, 10, 7, and 8, with a mean of 11.9. Middle latitude A Index was 6, 11, 24, 15, 11, 9, and 8, with a mean of 12. NNNN /EX | 
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