Tad Cook, K7RA, Seattle, reports: Although solar activity was generally lower this week, new sunspots appeared. A sunspot group emerged on February 10, two more on February 11, two more on February 14 and three more on February 16, when the daily sunspot number rose to 111, the highest value for this reporting week and well above the weekly average, which was 75.3. The average for the previous week was 83.9.
The February 16 count of 111 was the highest since the end of 2021, when sunspot numbers went as high as 147 following a few days with no sunspots at all.
Average daily solar flux declined from 126 to 110.1. Average daily planetary A index went from 14.4 to 13, and average daily middle latitude A index declined just 1.3 points to 8.3.
Why do we care about sunspot numbers? Because high values correlate with greater density in the ionosphere, which gives us better propagation at higher frequencies. Sixty-four years ago, sunspot numbers were so high that hams saw worldwide around-the-clock propagation on 10 meters. Sunspot numbers have never been so high before or since.
Predicted solar flux over the next month is 105 on February 17 – 18; 108 on February 19 – 27; 110 on February 28; 115 on March 1 – 2; 112 and 110 on March 3 – 4; 108 on March 5 – 8; 105 on March 9 – 11; 103 on March 12 – 13; 100 on March 14; 98 on March 15 – 16; 102 on March 17 – 19; 104 on March 20 – 22, and 108 on March 23 – 26.
Predicted planetary A index is 5 on February 17 – 18; 15, 18, and 15 on February 19 – 21; 8 on February 22 – 23; 15 and 10 on February 24 – 25; 5 on February 26 – March 2; 12, 15, 10, and 8 on March 3 – 6; 5 on March 7 – 10; then 15, 12, and 10 on March 11 – 13; 5 on March 14 – 18, and 8, 5, 12, 15, and 10 on March 19 – 23.
Sunspot numbers for February 10 – 16 were 78, 86, 54, 53, 72, 73, and 111, with a mean of 75.3. The 10.7-centimeter flux was 118, 113.1, 110.5, 105.4, 106.5, 114.3, and 102.9, with a mean of 110.1. Estimated planetary A indices were 21, 20, 13, 15, 8, 5, and 9, with a mean of 13. Middle latitude A index was 12, 12, 10, 9, 6, 3, and 6, with a mean of 8.3.
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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