Tad Cook, K7RA, of Seattle, Washington, reports for this week’s ARRL Propagation Bulletin:
Sunspot activity rose this week, as the average daily sunspot numbers increased from 68 to 105.1.
But solar flux? Not so much. The average daily solar flux rose from 134.3 to 138.4.
So, the sunspot average rose 55% and solar flux rose only 3%. We usually expect the numbers to track closer.
Tuesday, September 27, had lots of geomagnetic activity, with the planetary A index at 24 and middle latitude at 33. At www.spaceweather.com, blamed an unexpected CME for this activity. They also reported a huge sunspot beyond the sun’s eastern horizon and a helioseismic image at https://bit.ly/3ftpTIN.
The Australian Space Weather Forecasting Centre issued a geomagnetic warning at 2146 UTC on September 28, stating, “Geomagnetic 27-day recurrence patterns indicate that G1 geomagnetic activity is likely during the interval between September 30 and October 2. INCREASED GEOMAGNETIC ACTIVITY EXPECTED DUE TO CORONAL HOLE HIGH SPEED WIND STREAM.”
Predicted solar flux is 135 on September 29; 130 on September 30 through October 1; 125 on October 2 – 3; 120 on October 4 – 5; 132 on October 6 – 7; 135, 130, 128, and 132 on October 8 – 11; 136 on October 12 – 13; 138, 140, 138, and 135 on October 14 – 17; 132, 130, 128, and 125 on October 18 – 21; 130, 140, 142, and 145 on October 22 – 25, and 140, 135, 130, 125, 128, and 130 on October 26 – 31.
Planetary A index is predicted at 8, 20, 60, and 40 on September 29 through October 2; 20, 18, 16, and 10 on October 3 – 6; 8 on October 7 – 14; 10 on October 15 – 16; 8 on October 17 – 19; 12 on October 20 – 21; 8 on October 22 – 23; 10 on October 24 – 25, and 8 on October 26 – 27. Then, in a recurrent disturbance as the sun rotates into the same position as weeks earlier, 25, 50, 30, 20, 12, and 10 on October 28 through November 2.
Sunspot numbers for September 22 through 28, were 99, 111, 128, 96, 120, 110, and 72, with a mean of 105.1. The 10.7-centimeter flux was 136.7, 146.3, 146.5, 134.7, 135.1, 134.5, and 134.8, with a mean of 138.4. Estimated planetary A indices were 6, 12, 13, 7, 6, 24, and 5, with a mean of 10.4. Middle latitude A index was 5, 12, 10, 5, 5, 33, and 3, with a mean of 10.4.
Send your tips, questions, or comments to k7ra@arrl.net.