Like last week, eight new sunspot groups emerged this reporting week, September 7 – 13, 2023.
One appeared on September 7, another on September 9, four more on
September 10, another on September 11, and one more on September 12.
Solar activity made a nice comeback, with average daily sunspot numbers rising from 95.4 to 138.1, and solar flux increasing from 137.6 to 159.9.
The most active geomagnetic day was September 12, when the planetary A index was 25. A “stealth CME” with an aurora visible as far south as Missouri was reported on spaceweather.com.
The average daily planetary A index decreased from 15.4 to 10.4, and middle latitude numbers decreased from 16.3 to 11.3.
The autumnal equinox in the Northern Hemisphere is on September 22 — just a week away.
It seems that the next sustained short-term peak in solar flux is a few weeks off, with values between 150 and 155 on October 12 – 17, although it’s expected to reach 150 on September 23 – 24.
The forecast shows the solar flux at 145, 145, 148, 145, and 145 on September 14 – 18; 148 on September 19 – 20; 145 on September 21 – 22; 150 on September 23 – 24; 145 on September 25; 140 on September 26 – 27; 135 on September 28 – 30; 130, 135, 130, and 135 on October 1 – 4; 140 on October 5 – 6, and 135 on October 7 – 8.
Predicted
planetary A index is 12 and 15 on September 14 – 15; 8 on September 16 – 17; 5,
5, and 10 on September 18 – 20; 5, 5, and 12 on September 21 – 23; 5 on
September 24 – 27; 8, 12, and 8 on September 28 – 30, and 5 on October 1 – 8.
Sunspot numbers for
September 7 – 13, 2023, were 135, 123, 119, 167, 173, 141, and 109, with a mean
of 138.1. The 10.7-centimeter flux was 160.8, 160.9, 161.4, 163.9, 176.4,
153.5, and 142.6, with a mean of 159.9. Estimated planetary A indices were 6,
6, 8, 4, 7, 25, and 17, with a mean of 10.4. The middle latitude A index was
11, 8, 12, 6, 8, 17, and 17, with a mean of 11.3.