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The K7RA Solar Update

Tad Cook, K7RA, Seattle, reports: Solar activity is on the upswing this week. Average daily sunspot numbers increased from 21.7 to 50.6, with a high of 77 last Saturday, September 28. Average daily solar flux rose from 78.5 to 88.

Average daily planetary A index increased from 4.7 to 9.6, and average daily middle latitude A index went from 5.7 to 10.7. Geomagnetic activity peaked August 27 – 28 due to a coronal mass ejection.

New sunspot regions appeared on August 26 and 27, and on September 2 Spaceweather.com reported, “New Sunspot, Rapidly Growing” to announce the emergence of AR2863.

Predicted solar flux looks promising, particularly after mid – September, at 85 and 82 on September 3 – 4; 80 on September 5 – 6; 78 on September 7; 75 on September 8 – 10; 80 on September 11 – 14; 85 on September 15; 90 on September 16 – 30; 85 on October 1, and 80 on October 2 – 10. Flux values rise to 90 again after October 12 in this forecast from September 2.

Predicted planetary A index is 8, 5, 10, and 8 on September 3 – 6; 5 on September 7 – 10; 10 and 8 on September 11 – 12; 5 on September 13 – 20; 8 on September 21; 5 on September 22 – 25; then a big jump to 25, 8, 18, 8, and 12 on September 26 – 30, back to 5 on October 1 – 7, and then 10 and 8 on October 8 – 9.

Here’s the geomagnetic activity forecast for September 3 – 29, from F.K. Janda, OK1HH.

The geomagnetic field will be:

quiet on September 7 – 8, 10, 14 – 15, 17 – 18, 28 – 29
quiet to unsettled on September 4 – 5, 13, 16, 19, 22, 25, 27
quiet to active on September 3, 6, 9, 11 – 12, 20 – 21, 26
unsettled to active on September 23 ( – 24)
active to disturbed — nothing predicted
Remarks:

* Parentheses mean lower probability of activity enhancement.

* The situation is confusing, the configuration of active regions and coronal holes is variable, so it’s not possible to make a reasonably reliable forecast. This occasionally happens before solar activity rises.

The autumnal equinox will be on Wednesday, September 22, in the Northern Hemisphere, always a welcome event for HF propagation. Solar flux is forecast to be higher at that time, also a good sign.

Sunspot numbers for August 26 – September 1, 2021 were 47, 73, 77, 44, 41, 37, and 35, with a mean of 50.6. The 10.7 centimeter flux was 88.6, 89.5, 89.9, 88.7, 90.6, 84.4, and 84.2, with a mean of 88. Estimated planetary A indices were 6, 20, 14, 8, 7, 7, and 5, with a mean of 9.6. Middle latitude A index was 6, 19, 17, 9, 9, 9, and 6, with a mean of 10.7.

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

A propagation bulletin archive is available. For customizable propagation charts, visit the VOACAP Online for Ham Radio website.

Instructions for starting or ending email distribution of ARRL bulletins are on the ARRL website.

Share your reports and observations. (arrl.org)

 

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