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The K7RA Solar Update


We saw a modest increase in solar activity in this reporting week, May 4-10.

Average daily sunspot numbers nudged up from 114 to 119.3, and average daily solar flux from 151.5 to 167.1  

Average daily planetary A index changed from 13.6 to 15.1, and average middle latitude A index remained the same, 11.9.

Predicted solar flux is 160 on May 12-13, then 155, 150 and 150 on May 14-16, 145 on May 17-18, 155 on May 19-21, 150 on May 22, 145 on May 23-25, then 140 and 145 on May 26-27, 155 on May 29-30, 160 on May 31 through June 1, 155 on June 2-3, 160 on June 4-7, then 165, 160, 150, 145 and 150 on June 8-12, and 155 on June 13-17.  

Predicted planetary A index is 30, 12 and 8 on May 12-14, 5 on May 15-22, then 12 and 20 on May 23-24, 15 on May 25-26, 10 on May 27-28, 8 on May 29, 5 on May 30 through June 1, then 16, 12, 16 and 12 on June 2-5, 8 on June 6-8, and 5 on June 9- 18, then 12 and 20 on June 19-20.

Stormy space weather: .

BBC on viewing aurora:


Jon, N0JK wrote on May 9:  

"Good 6 Meter Es, TEP May 7 FT8 from northeast Kansas.  

I worked CX2AQ and LU5FF from home with an attic dipole on FT8. This around 2115 UTC. Not strong, but solid contacts. I then set up portable.

Worked CE2SV and CE3SX. CE3SX called me, also FT8. Had difficulty keeping yagi up due to gusty winds. On ON4KST Dale, CE2SV noted:  

00:11:46 N0JK Jon, A struggle on my side, wind blew antenna down several times and broke director. Duct tape to the rescue.  

00:11:07 N0JK Jon (CE2SV) Dale - Thank you for the contact.  

22:42:46 CE2SV Dale (N0JK) Finally Jon ... TU   

Gary, N0KQY observes there is a 'consistent time frame' for Es -- TEP to South America from the Midwest. Best seems to be 2000-0000 UTC." Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere May 12-18, 2023 from F.K. Janda, OK1HH.  

"The more vivid and complex solar activity is, the less predictable it is. The same is valid for its effects in the Earth's magnetosphere and ionosphere.  

This was particularly true of the solar flares of May 4 and 5, and also of the G2 class geomagnetic storm with auroras. The CMEs overlapping each other were difficult to separate.  

Another CME that struck the Earth on May 7 (1544 UTC) was expected but, contrary to predictions, did not cause a significant storm. Another Coronal Mass Ejection (CME) hit the Earth on May 9 at 2310 UTC.  Shortly before, AR3296 (with reversed magnetic polarity and thus violating Hale's law) released a double solar flare.  

The consequence was the Dellinger effect (a shortwave fade) up to 25 MHz from 1900-2100 UTC. Another CME followed with a velocity of over 1,000 km/s (2.24 million mph). Shock waves at its leading edge accelerated protons to nearly the speed of light, making them 'relativistic particles', for which time passes more slowly. They can reach the Earth and affect the ionosphere.  

These lines are written on the afternoon of 11 May UTC, when the particles from the eruption of 9 May with a maximum at 1858 UTC are expected to arrive.  

Large AR3296 and AR3297 will set behind the northwestern edge of the solar disc in a few days. In the meantime, AR3301 and AR3302 emerged in the northeast.  

Helioseismological observations indicate another large sunspot group will follow them out. Therefore, the current variable nature of the evolution with numerous disturbances will continue."  

Five days ago from Dr. Tamitha Skov:  

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 .

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 May 4 through 10, 2023 were 139, 90, 99, 99, 103, 151, and 154, with a mean of 119.3. 10.7 cm flux was 162, 161.9, 151.8, 157.2, 171.9, 194.7, and 170.1, with a mean of 167.1. Estimated planetary A indices were 6, 5, 30, 9, 16, 14, and 26, with a mean of 15.1. Middle latitude A index was 7, 4, 21, 8, 13, 11, and 19, with a mean of 11.9.



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