Tad Cook, K7RA, Seattle, reports:

Last week, we reported a big increase in solar activity with the daily sunspot number reaching 124, but by the end of that week, all the sunspots had disappeared. The sun was blank for several days, but then, sunspots returned on September 19.

Average daily sunspot numbers were 28.7 this week, below the 58.3 average reported a week earlier. Average daily solar flux was down by nine points, from 87.4 to 78.4.

Geomagnetic indicators were higher, with the highest activity on September 17, when the planetary A index was 24 due to a minor geomagnetic storm triggered by a weak coronal mass ejection (CME). Average daily planetary A index for the week increased from 7 to 9.1, and average middle-latitude A index went from 6.9 to 8.4.

Predicted solar flux for the next month is 90 on September 23; 95 on September 24 – 25; 98 and 95 on September 26 – 27; 90 on September 28 – 29; 84 on September 30 – October 5; 82 on October 6; 80 on October 7 – 8; 78 on October 9 – 11; 75 on October 12 – 20; 80 on October 21 – 22; 82 on October 23 – 25; 84 and 82 on October 26 – 27, and 84 on October 28 – November 1.

Predicted planetary A index is 12, 8, and 15 on September 23 – 25; 8 on September 26 – 27; 12 on September 28; 10 on September 29 – 30; 5 on October 1 – 3; 8 and 12 on October 4 – 5; 5 on October 6 – 9; 12 on October 10; 5 on October 11 – 17; 8 on October 18 – 19; 10, 8, and 12 on October 20 – 22; 10 on October 23 – 24, and 5 on October 25 – 30.

ARRL News Letter on September 21, 2021