Tad Cook, K7RA, of Seattle, Washington, reports for this week’s ARRL Propagation Bulletin:
Geomagnetic disturbances were down this week, but so were sunspot numbers and solar flux.
Average daily sunspot numbers declined from 92.7 to 68, and average daily solar flux declined from 141.3 to 134.3.
Six new sunspot groups appeared this week, the first on September 15, two more on September 19, another on September 20, and two more on September 21.
Predicted solar flux is 140 and 138 on September 22 – 23; 130 on September 24 – 27; 120 on September 28; 122 on September 29 through October 2; 120 again on October 3; 122 on October 4 – 7; 125, 122, and 120 on October 8 – 10; 118 on October 11 – 12; 116 on October 13 – 15; 138 on October 16; 135 on October 17 – 18, and 133, 128, 126, 130, and 125 on October 19 – 23.
Predicted planetary A index is 10 and 20 on September 22 – 23; 15 on September 24 – 25; 8 on September 26 – 29; 22, 50, 30, and 20 on September 30 through October 3; 12, 15, 12, and 10 on October 4 – 7; 8, 8, 5, and 8 on October 8 – 11; 5 on October 12 – 14; 12, 10, 5, 5, 20, 18, and 12 on October 15 – 21, and 8 on October 22 – 26.
The above predictions were made by the Offutt Air Force Base.
For information on whether sunspots are really black, visit www.livescience.com/why-are-sunspots-black.
I’m pleased to report that the 2022 Autumnal Equinox is Friday, September 23, at 0104 UTC. Both the Northern and Southern Hemispheres will be bathed in equal measures of solar radiation, which is good for HF propagation.
Sunspot numbers for September 15 through 21 were 71, 64, 76, 51, 74, 70, and 70, with a mean of 68. The 10.7-centimeter flux was 139.7, 131.1, 131.5, 136.1, 127.9, 137.2, and 136.9, with a mean of 134.3. Estimated planetary A indices were 6, 4, 5, 11, 11, 8, and 5, with a mean of 7.1. Middle latitude A index was 8, 5, 5, 9, 7, 6, and 4, with a mean of 6.9.
Send your tips, questions, or comments to k7ra@arrl.net.
A comprehensive K7RA Solar Update is posted Fridays on the ARRL website. For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…” and check out the Propagation Page of Carl Luetzelschwab, K9LA.
A propagation bulletin archive is available. For customizable propagation charts, visit the VOACAP Online for Ham Radio website.
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