Tad Cook, K7RA, Seattle, Washington, reports:
Solar activity took a dramatic plunge over the recent reporting week (June 23 – 29), but geomagnetic activity stayed the same. ARRLField Day weekend saw rising geomagnetic numbers, with the planetary A index at 8, 16, and 23, Friday through Sunday.
On Sunday, June 25, 2022, the geomagnetic activity was a problem, although not severe, with many stations on Field Day reporting increased absorption. The planetary K index peaked at 5 (a big number) at the end of the day on Saturday (UTC time) and continued into the early hours of Sunday, which was early Saturday evening on the West Coast.
This happened because of a crack in the Earth’s magnetosphere, detailed here:
Compared to the previous 7 days, average daily sunspot numbers declined from 124.6 to 49.1, while average daily solar flux dropped from 140.5 to 105.3.
Planetary and middle latitude A index averages were both the same as the previous week, all numbers around 11.
The prediction from the United States Air Force (USAF) 557th Weather Wing is not very optimistic, with solar flux peaking at 140 on July 11 – 16.
The prediction shows 10.7-centimeter solar flux at 90 on June 30 and July 1; 95 on July 2; 105 on July 3 – 7; 130 on July 8 – 9; 135 on July 10; 140 on July 11 – 16; 135, 130, 125, and 120 on July 17 – 20; 115, 110, 105, and 100 on July 21 – 24; 95 on July 25 – 26; 100 on July 27 – 29, and 105, 110, 115, and 120 on July 30 through August 2.
Predicted planetary A index is 8, 10, and 8 on June 30 through July 2; 5 on July 3 – 7; 8, 8, 12, and 8 on July 8 – 11; 5 on July 12 – 13; 12 on July 14 – 16; 10 on July 17; 8 on July 18 – 21; 12, 15, 15, and 10 on July 22 – 25, and 5 on July 26 through August 4.
In Friday’s bulletin, look for updated forecasts and observations emailed by readers to k7ra@arrl.net.
Sunspot numbers for June 23 through 29 were 69, 60, 31, 33, 32, 71, and 48, with a mean of 49.1. The 10.7-centimeter flux was 121.4, 115.4, 108.1, 102, 98.2, 96.1, and 96.2, with a mean of 105.3. Estimated planetary A indices were 10, 8, 16, 23, 12, 8, and 6, with a mean of 11.9. Middle latitude A index was 12, 8, 14, 15, 15, 11, and 7, with a mean of 11.7.
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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