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The K7RA Solar Update


Average daily sunspot numbers declined, but average daily solar flux increased.  Sunspot averages were 181.9 last week, and 130.6 this week.  Average daily solar flux increased from 179.4 to 190.5.

Two new sunspot groups emerged on July 14, three more on July 17 and another two on July 19.

Average daily planetary and middle latitude A index were both 12.9 this week, rising from 8.6 and 8.1.

Predicted solar flux is 185 on July 21-23, then 180, 178, 175 and 170 on July 24-27, 165 on July 28-29, 170 on July 30-31, 165 on August 1-4, then 170, 175, 175 and 170 on August 5-8, 165 on August 9-11, 170 on August 12, 175 on August 13-14, and 170 on August 15-19, 160 on August 20-23, 165 on August 24-25, then 170 on August 26-27 and 165 on August 28-31.

Predicted planetary A index is 20, 12, 8, 12 and 10 on July 21-25, 5 on July 26 through August 2, then 10 and 8 on August 3-4, 5 on August 5-14, then 12, 8 and 8 on August 15-17, and 5 on August 18-29.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere for July 20, 2023 from OK1HH.

"We've seen another seven days of mostly moderate solar activity, with almost daily eruptions of moderate magnitude on the Sun.  Some of these have been the source of CMEs.  If the Earth has been affected by them, a geomagnetic disturbance followed, with a drop in MUF and a worsening of HF propagation in the process.

As predicted, the expected CME hit the Earth's magnetic field on the afternoon of 14 July (as part of the Bastille Day celebrations, but not nearly as strongly as in 2000).

Another CME left the Sun on 14 July, and yet another on July 15. Because the cloud of later ejected solar plasma was faster, it cannibalized the previous CME.  Together, they hit the Earth on July 18.

But by then AR3363 had already produced a significant long-lasting M6-class solar flare, and energetic protons accelerated by this flare reached the Earth and caused a radiation storm.  Although MUFs were quite high, HF conditions were adversely affected by frequent occurrences of attenuation.

Another CME hit the Earth on 20 July, registered by the Earth's magnetic field at 1708 UTC.

Further developments were predicted up to G1 to G2 class geomagnetic storms, with a small probability also of G3, but by then this report will have been completed and sent out.

Finally, just a little note on the consequences of global change: it has been manifested in the last eleven-year cycles, in the Earth's troposphere it is the result of warming, but in the ionosphere it is rather the opposite.  It has been the subject of a number of scientific papers in recent years.

It is crucial for us, for amateur radio practice, that the current MUFs are lower than those calculated from sunspot counts for most of the twentieth century.  Therefore, we should input Ri (or solar flux SFU) into forecast programs lower than what is currently measured and published.

F.K. Janda, A.R.S. OK1HH  "

News from N8II in West Virginia.

"The bands are in much better shape than most hams realize; activity levels are normally quite low this summer.  In the IARU contest I observed 15M open to Europe through 0300 UTC and I had QSOs with Indonesia, China, Nepal, Japan, Central/Western Siberia, Kazakhstan, and the Philippines in the 2300-0300 UTC period.  I copied GR2HQ (Great Britain HQ station) on 10M CW at 0140 UTC.  At 1100 UTC on 15M EU and Central/West Asia were very loud and I started running a pile up on CW.

The Far East was also in on 15M around 1400 UTC Saturday when I worked a loud Japanese station.

During the evening/night EU signals were extremely loud on 20M.  I also worked a few EU on 10M 1300-1400 UTC Saturday thanks to Sporadic E and also caught Z30HQ (Macedonia HQ) on 10M CW Sunday about 1130 UTC.  I worked 697 QSOs concentrating on DX on the high bands in less than 12 hours with 100 W.

Africa is workable on 10-15M well into our evening as are South Pacific stations.

Sporadic E this year seems somewhat attenuated, but Es was good from here and great from the Central/Western USA during the June VHF contest.  I made about 170 CW/SSB QSOs."

CNN presented a smart piece on the sunspot cycle peaking sooner than expected.

Double peaked flare.

Astronomy club observes sunspots.


Scientific American.

Early peak.

Cannibal eruption.

Great video of eruption.

The latest from Space Weather Woman Dr. Tamitha Skov, WX6SWW.

Send your tips, reports, observations, questions and comments to .  When reporting observations, don't forget to tell us which mode you were operating.

For more information concerning shortwave radio propagation, see  and the ARRL Technical Information Service at  .  For an explanation of numbers used in this bulletin, see  .

Also, check this article from September, 2002 QST:

An archive of past propagation bulletins is at  . More good information and tutorials on propagation are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for July 13 through 19, 2023 were 146, 141, 96, 99, 149, 142, and 141, with a mean of 130.6.  10.7 cm flux was 202.9, 180.6, 178.5, 184.3, 180, 218.5, and 188.9, with a mean of 190.5. Estimated planetary A indices were 7, 20, 8, 10, 24, 16, and 5, with a mean of 12.9.  Middle latitude A index was 9, 17, 9, 13, 19, 16, and 7, with a mean of 12.9.



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