St. Patrick’s Day Report

Tad Cook, K7RA, Seattle, Washington reports: On March 11 at 0431 UTC, Australia’s Space Forecast Centre issued a warning. “A slow coronal mass ejection has been observed late on 10 March, and event modeling suggests arrival at the Earth late on 13 March. Increased geomagnetic activity is expected for 14 March 2022.”

We observed an active sun this week. Geomagnetic indicators peaked on Saturday, March 5, when Alaska’s high-latitude college A index reached 42.

Again this week, sunspots covered the sun every day. Average daily sunspot numbers rose from 44 to 87.4, and average daily solar flux went from 98.5 to 115.5. Geomagnetic indicators were also higher. Average daily planetary A index increased from 7.3 to 11.4.

The vernal equinox is in a little over a week, 1533 UTC on Sunday, March 20, when Earth will be bathed in an equal amount of solar radiation over both Southern and Northern Hemispheres, good for HF propagation. It is the first day of spring in the Northern Hemisphere, and fall in the southern.

Predicted solar flux is 120 on March 11 – 12; 115 on March 13; 110 on March 14 – 16; 105 on March 17; 100 on March 18 – 21; then 101 and 103 on March 22 – 23; 104 on March 24 – 27; then 110, 115, and 116 on March 28 – 30; 118 on March 31 through April 1; 120 on April 2; 116 on April 3 – 4; then 115 and 112 on April 5 – 6; 110 on April 7 – 9; then 108, 102, 98, and 99 on April 10 – 13; then 100 on April 14 – 17.

Predicted planetary A index is 12 on March 11; 5 on March 12 – 13; then 10, 18, 15, 5, and 8 on March 14 – 18; then 12 on March 19 – 20; 15 on March 21; 7 on March 22 – 24; then 5, 10 and 8, on March 25 – 27; 5 on March 28 – 29; then 10, 12, 25, 20, and 10 on March 30 through April 3; 5 on April 4 – 6; then 15, 20, and 12 on April 7 – 9; 5 on April 10 – 13; then 8 on April 14, and 10 on April 15 – 16.

Sunspot numbers for March 3 through 9, 2022 were 92, 77, 95, 82, 84, 93, and 89, with a mean of 87.4. 10.7-centimeter flux was 110.9, 113.1, 120.1, 115.7, 118.3, 115.3, and 114.8, with a mean of 115.5. Estimated planetary A indices were 5, 10, 27, 18, 9, 6, and 5, with a mean of 11.4. Middle latitude A index was 3, 7, 19, 13, 7, 5, and 4, 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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