09/03/2021

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[1] 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:

o quiet on September 7 - 8, 10, 14 - 15, 17 - 18, 28 - 29
o quiet to unsettled on September 4 - 5, 13, 16, 19, 22, 25, 27
o quiet to active on September 3, 6, 9, 11 - 12, 20 - 21, 26
o unsettled to active on September 23 ( - 24)
o 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[2] the ARRL Technical
Information Service, read[3] "What the Numbers Mean...," and check out this
propagation page[4].

A propagation bulletin archive[5] is available. For customizable propagation
charts, visit the VOACAP Online for Ham Radio[6] website.

Instructions[7] for starting or ending email distribution of ARRL bulletins are
on the ARRL website.

Share[8] your reports and observations.

[1] http://www.spaceweather.com/
[2] http://arrl.org/propagation-of-rf-signals
[3] http://arrl.org/the-sun-the-earth-the-ionosphere
[4] http://k9la.us/
[5] http://arrl.org/w1aw-bulletins-archive-propagation
[6] https://www.voacap.com/hf/
[7] http://arrl.org/bulletins
[8] mailto:k7ra@arrl.net

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