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The K7RA Solar Update

09/10/2021

Tad Cook, K7RA, Seattle, reports: Sunspot activity increased dramatically this week.

Over the course of the reporting week, sunspot numbers peaked at 87 on Wednesday, September 8; the day before, solar flux peaked at 101.2.

The average daily sunspot numbers rose by 14, to 64.6, while the average daily solar flux increased from 88 to 92.9. New sunspots appeared on September 2 and September 3, and three more new sunspot groups arrived on September 4. Another new one appeared on September 8, and on that day the total sunspot area was 1,000 micro-hemispheres.

On September 9, I was shocked to see the daily sunspot number at 124 and the total sunspot area hit 1,030 micro-hemispheres. I don’t believe we’ve seen activity like this in nearly 6 years, when the daily sunspot number hit 125 on September 29, 2015.

We saw similar large total sunspot area numbers last November 25 – 26 — 1,180 and 1,020 micro-hemispheres. Sunspot numbers were 40 and 43 on those days, but a few days later on November 29 the sunspot number shot to 84.

Both the daily planetary and middle latitude A index reached highs of 14 on September 8. The averages were 7 and 7.7, down from 9.6 and 10.7 in last week’s planetary and middle latitude readings.

Predicted solar flux seems quite promising, at 100 on September 10 – 11; 98 on September 12 – 13; 95 on September 14 – 17; 85 on September 18; 88 on September 19 – 23; 90 on September 24 – 28; 88 on September 29 – October 1; 86 on October 2; 90 on October 3 – 6; 92 and 90 on October 7 – 8, and 85 on October 9 – 15. Flux values are expected to rise to 90 again after October 20.

Predicted planetary A index is 5, 8, and 8 on September 10 – 12; 5 on September 13 – 20; 8 on September 21; 5 on September 22 – October 1; 8 again on October 2 – 3, and 5 on October 4 – 17.

On Sunday September 5, Spaceweather.com reported, “For most of the past 3 years, the sun has been absolutely blank. Today the sun has six sunspot groups. They’re popping up all over the solar disk.

“The sudden profusion of so many sunspots is a sign of strength for young Solar Cycle 25. The solar cycle is actually running ahead of schedule. NOAA and NASA predicted that it will peak in the year 2025. Outbreaks like this one support the idea that solar max could come a year early.”

On September 8, Spaceweather.com reported a shortwave blackout over the Pacific Rim caused by a coronal mass ejection (CME) on September 8 at 1736 UTC.

Here’s the most recent forecast from the Space Weather Woman, Tamitha Skov, WX6SWW, although by now it is a bit out of date.

This is an interesting article about recent solar activity, but it is plagued with many popups.

Recently in this bulletin we mentioned the US Postal Service issuing stamps with solar images. This article from June which gives much more detail on the creation of the stamps.

Sunspot numbers for September 2 – 8 were 33, 33, 68, 66, 80, 85, and 87, with a mean of 64.6. The 10.7-centimeter flux was 85.8, 83.8, 86.5, 93.3, 99.5, 101.2, and 100.4, with a mean of 92.9. Estimated planetary A indices were 4, 6, 5, 6, 6, 8, and 14, with a mean of 7. Middle latitude A index was 3, 6, 5, 8, 8, 10, and 14, with a mean of 7.7.

For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check out this propagation page.

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