SB PROP @ ARL $ARLP031 ARLP031 Propagation de K7RA ZCZC AP31 QST de W1AW Propagation Forecast Bulletin 31 ARLP031 From Tad Cook, K7RA Seattle, WA August 16, 2024 To all radio amateurs SB PROP ARL ARLP031 ARLP031 Propagation de K7RA With sunspot numbers and solar flux at times both above 300, recent daily space weather has been exciting for radio amateurs who watch the sun. We like higher activity because it correlates with a dense ionosphere, bringing with it better conditions on higher frequencies. This extreme activity also comes with greater geomagnetic disturbance, which cause higher absorption of HF signals. For example, on August 12 the solar flux was 272.4 and sunspot number was 245. Middle latitude A index was 51 and planetary A index was 122, very high values indicating the G4 geomagnetic storm. Seven new sunspot groups appeared this week, two on August 8, four on August 11 and one on August 14. On August 9 the daily sunspot number was 382, the highest in two decades. Average daily sunspot numbers rose from 222.3 to 255, while average daily solar flux increased from 255.3 to 284.9. Average daily planetary A index went from 15.7 to 28.6, and average daily middle latitude A index (measured at a single magnetometer in Virginia) from 13.4 to 17.9. The solar flux outlook for the next few weeks looks promising, with values peaking at 300 in the first week of September. Predicted values from forecasters Jones and Kiser at the US Air Force are 230, 225 and 220 on August 16-18, 215 on August 19-20, then 210, 205, 200 and 210 on August 21-24, 220 on August 25-26, 235 on August 27-28, 245 on August 29-30, then 240, 245 and 270 on August 31 through September 2, 300 on September 3-5, 290 on September 6-7, 280 on September 8, and 270 on September 9-11, then 260 on September 12-14, then 250, 240, 230, 210, 200 and 210 on September 15-20, and 220 on September 21-22. Predicted planetary A index is 10, 18, 30, 25 and 10 on August 16-20, then 5, 5 and 8 on August 21-23, then 5 on August 24 to September 17, then 18 and 12 on September 18-19, and 5 on September 10 until November. Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere for August 15, 2024 from F. K. Janda, OK1HH. The current maximum of the "eleven-year" solar cycle is gradually surpassing all expectations and all predictions. Medium-mass flares (M-class) are observed almost daily and are often intense enough to silence radio signals at least in the longer part of short waves by increasing the attenuation in the lower ionosphere. Large solar flares (X-class) are no exception. They usually (shortly) knock out the entire shortwave range. Many eruptions are accompanied by a particle cloud ejection (CME). If this happens near or west of the central meridian, it is very likely to "hit" the globe and cause a geomagnetic disturbance. In the case of multiple particle clouds flying toward the Earth at the same time, the first one may clear the way for the following ones, causing an extremely strong disturbance. Which is exactly what we saw on August 11-12. The geomagnetic disturbance reached G4 level, while not only auroras were observed in mid-latitudes during the disturbance, but also a phenomenon known as STEVE (Strong Thermal Emission Velocity Enhancement), until relatively recently confused with auroras. We observe it as a colored tilted ribbon. Thanks to the simultaneous peak of the Perseids meteor shower, we were able to witness a truly extraordinary spectacle. The height of the highest critical frequencies of the f0F2 layer, and thus the MUF, was on average at an eleven-year low of solar activity on August 12. However, with the difference that as the radio wave passed through the ionosphere, a large attenuation was produced, largely due to scattering on inhomogeneities. The improvement in propagation conditions was slow and gradual. A slightly better 13 August was followed by a deterioration on 14 August. Situation was only slightly above average on 15 August. But with that said, we already knew of other CMEs heading towards Earth. We don't expect a drop in solar activity anytime soon, if only because we know of other active regions on the far side of the Sun thanks to helioseismological observations. Soon we will be able to observe them on the eastern edge of the solar disk. W3LPL wrote in an email: "Ain't this solar maximum great? Solar Cycle 25 is now much, much stronger than anyone anticipated, and it s slowly growing stronger through at least this weekend. Today's Wednesday estimated international sunspot number is 281. It s increasingly likely that we'll have widespread coast-to-coast and worldwide 6 meter F2 propagation during about half of the days between late October and at least early February. Widespread F2 openings are likely to bring 6 meter CW and SSB to life like we haven't experienced in more than 20 years. The first sign of enhanced 6 meter F2 will be increasingly frequent TEP from Europe and North America to South America and the South Atlantic islands. TEP may begin very sporadically by late August and become increasingly frequent later in September and especially during October. Coast-to-coast F2 propagation and propagation crossing the Atlantic to Europe and Africa may begin sporadically during September and October and become frequent and long lasting by early November. Effective 6 meter antennas can be very small. 3 element Yagis are small, lightweight and very effective. 20 foot antenna height is adequate but sloping terrain or higher antennas perform much better. Heights higher that 50 feet are not necessary and in many cases perform poorly. Are you ready for this once in a lifetime experience?" I want to remind everyone of this useful web site: https://prop.kc2g.com Record breaking number of sunspots: https://www.space.com/sunspots-solar-cycle-25 https://tinyurl.com/k9cnbtt8 Sky & Telescope: https://tinyurl.com/musyznst Massive flare: https://bit.ly/4fPW1Bp Newsweek on aurora: https://tinyurl.com/3wnckehs Cycle 26: https://tinyurl.com/3jdhyekc Forbes claims quarter century max: https://tinyurl.com/yhm398ph Red Deer, Alberta: https://tinyurl.com/y5a7sv3f Great solar image: https://tinyurl.com/yc84azws New report from Tamitha Skov: https://youtu.be/yd1gEZoYpsM 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 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 subscriptions to ARRL bulletins are at www.arrl.org/bulletins. Sunspot numbers for August 8 through 14 2024 were 337, 382, 234, 194, 245, 199, and 194, with a mean of 255. 10.7 cm flux was 336, 305.5, 291.1, 281.5, 272.4, 259.9, and 248.2, with a mean of 284.9. Estimated planetary A indices were 7, 7, 7, 28, 122, 17, and 12, with a mean of 28.6. Middle latitude A Index was 11, 9, 8, 23, 51, 12, and 11, with a mean of 17.9. NNNN /EX | 
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