SB PROP @ ARL $ARLP027 ARLP027 Propagation de K7RA ZCZC AP27 QST de W1AW Propagation Forecast Bulletin 27 ARLP027 From Tad Cook, K7RA Seattle, WA July 19, 2024 To all radio amateurs SB PROP ARL ARLP027 ARLP027 Propagation de K7RA Big increase in solar activity this week, with average daily sunspot number rising from 129 to 215.9, and solar flux from 176.6 to 226.5. Fourteen new sunspot groups emerged. Two were on July 11, one on July 12, three on July 13, one on July 14, two more on July 15, three more on July 16 and two more on July 17. On Thursday (after the reporting week) the daily sunspot number was 276, the highest value for cycle 25, according to Jon Jones, K0JK. A new sunspot group appeared that day. Average planetary A index was quiet at 6, and the middle latitude number was 8. More quiet geomagnetic indicators are forecast for the entire month of August, with planetary A index predicted at 5 on every day. Predicted solar flux is 210 on July 19-21, 200 on July 22-25, 180 on July 26-27, 175 on July 28, 170 on July 29-31, 165 on August 1-2, then 170, 180 and 190 on August 3-5, 200 on August 6-11, and 230 on August 12-14, then 210 on August 15, 200 on August 16-18, then 195 and 185 on August 19-20, and 180 on August 21-23. Predicted planetary A index is 8, 16, 20 and 8 on July 19-22, and 5 on July 23 through the entire month of August and possibly the first week in September. Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere for July 18, 2024. Increased solar flare activity continues. M-class eruptions are almost the order of the day and X-class eruptions are no exception. Their main source is currently the largest AR3751. While it is still in the southeast quadrant of the solar disk, it will cross the central meridian as early as July 19. After that the probability of an Earth impact by a possible CME will increase. In the southwest quadrant we observe five sunspot groups: AR 3742, AR3743, AR3745, AR3747 and AR3758, which were formed by the spill of the original extremely active May AR3664 (designated as AR3697, AR3723 in subsequent solar rotations). Solar activity remains high and geomagnetic disturbances are less frequent and do not last long. Ionospheric shortwave propagation conditions, although mostly slightly above average level, vary irregularly. The sporadic layer E will continue for a few more weeks. We will continue to see fading during the day, in particular at lower shortwave frequencies (on the 7 MHz band and much more often and longer on 3.5 MHz) during moderate flares. Entire shortwave bursts will die down here and there during the largest flares, especially long-lasting X-class flares. F. K. Janda, OK1HH Recent video from Tamitha Skov: https://youtu.be/GLBIY3bbdQE Solar Flare: https://bit.ly/3Wp9wjA Martian aurora: https://bit.ly/4cJ2L21 Blackouts: https://bit.ly/468L89c https://bit.ly/3LrTxex https://bit.ly/3Lx0ye6 https://bit.ly/3Y7Lgnq Cycle 26: https://bit.ly/3YaG02h 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: https://bit.ly/3Rc8Njt Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins. Sunspot numbers for July 11 through 17 2024 were 188, 162, 214, 217, 205, 250, and 275, with a mean of 215.9. 10.7 cm flux was 205, 209.7, 238.3, 233.9, 233.2, 241.9, and 223.8, with a mean of 226.5. Estimated planetary A indices were 6, 5, 4, 5, 7, 10, and 5, with a mean of 6. Middle latitude A Index was 7, 7, 6, 9, 8, 12, and 7, with a mean of 8. NNNN /EX | 
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