SB PROP @ ARL $ARLP023 ARLP023 Propagation de K7RA ZCZC AP23 QST de W1AW Propagation Forecast Bulletin 23 ARLP023 From Tad Cook, K7RA Seattle, WA June 21, 2024 To all radio amateurs SB PROP ARL ARLP023 ARLP023 Propagation de K7RA Sunspot numbers rose this week, with the average changing from 139.4 to 149.6, but average daily solar flux only shifted from 179.2 to 178. Only four sunspot groups emerged this week. There was one on June 15 and three on June 19. Average daily planetary A index only changed from 11.6 to 10.3. Predicted solar flux is 205 and 210 on June 21-22, then 200 June 23-27, then 190, 185, and 190, on June 28-30, then 190, 195, 190, 185 and 190 on July 1-5, 180 on July 6-7, 165 on July 8-9, 180 on July 10, then 170 on July 11-13, 175 on July 14, 180 on July 15-17, 175 on July 18-19, 190 on July 20-21, then 180, 175, 180, 190, 180, 185 and 190 on July 22-28. Predicted planetary A index is 10, 12 and 10 on June 21-23, then 5 on June 24-29, 8 on Jun 30 to July 1, then 5 on July 2-14, then 12, 8, 8, and 5 on July 15-18, 8 on July 19-20, and 5 on July 21-26, then 8 on July 27-28. Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - June 20, 2024, from OK1HH. F.K. Janda is going on vacation and will not have a report for us over the next few weeks. "Watching the Sun at its current 11-year peak of activity is certainly not boring. On the contrary, we are experiencing quite frequent surprises. For example, a week ago we observed an increased attenuation of radio waves in the polar region (PCA = POLAR CAP ABSORPTION EVENT), caused by protons coming from the far side of the Sun. Then, on 15 June (at 1157 UTC), a cloud of particles unexpectedly hit the Earth, triggering a weak G1 class geomagnetic storm. "Over the next few days, AR3712 became larger, followed by AR3713 and AR3716. All three of these large sunspot groups are already located in the western half of the solar disk, where particles from a possible larger flare are more likely to hit Earth. In addition, all three regions have an unstable magnetic field and are therefore more likely to have M- or X-class flares. "Of the largest sunspot groups observed this cycle, two will soon reappear on the eastern limb of the solar disk (in May they were designated AR3663 and AR3664). The first of these will begin to emerge on the solar disk this weekend. The second, and then largest group, will follow a few days after that. Fortunately, solar activity will remain high, but unfortunately, changes in propagation conditions will be harder to predict." From the European Space Agency: https://bit.ly/3VQt54j AR3712 and flares: https://bit.ly/3xiIGAa Reverse magnetic field: https://gigazine.net/gsc_news/en/20240617-sun-magnetic-field-flip/ This video about the Sun's corona is undated: https://www.dailymotion.com/video/x90o8gw Polar cap absorption event: https://bit.ly/3REcY7b https://bit.ly/3REhuTb Latest videos from Dr. Tamitha Skov, WX6SWW: https://youtu.be/J3XdqnWYNh4 https://youtu.be/tzfvKObBf_w This weekend is ARRL Field Day, and the forecast looks good, with high solar flux at 200 and 190. 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 www.arrl.org/propagation and the ARRL Technical Information Service web page at, www.arrl.org/propagation-of-rf-signals. For an explanation of numbers used in this bulletin, see www.arrl.org/the-sun-the-earth-the-ionosphere. An archive of past propagation bulletins is at www.arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us. Also, check this QST article on Solar Indices: https://bit.ly/3Rc8Njt Instructions for starting or ending email distribution of ARRL bulletins are at www.arrl.org/bulletins. Sunspot numbers for June 13 through 19 2024 were 142, 117, 134, 152, 171, 150, and 181, with a mean of 149.6. 10.7 cm flux was 170.1, 169, 170.7, 167.3, 179.9, 192.7, and 196, with a mean of 178. Estimated planetary A indices were 4, 6, 19, 13, 11, 10, and 9, with a mean of 10.3. Middle latitude A index was 5, 8, 18, 9, 11, 11, and 9, with a mean of 10.1. NNNN /EX |
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