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The K7RA Solar Update


Both average daily sunspot numbers and solar flux increased this week.  Average daily sunspot numbers rose from 118.6 to 133.4, while average solar flux went from 143.2 to 161.2.

Geomagnetic indicators were more active.  Average daily planetary A index went from 9.6 to 17.1, while average middle latitude A index rose from 9.6 to 14.4.

Predicted solar flux is 150 on May 26, 155 on May 27 and 28, then 150, 145, 140 and 135 on May 29 through June 1, 155 on June 2 to 4, then 160, 165, 160, 155, and 150 on June 5 to 9, 145 on June 10 and 11, 150 on June 12, 155 on June 13 and 14, 160 on June 15, 165 on June 16 and 17, then 160, 155 and 150 on June 18 to 20, 155 on June 21 and 22, then 160, 165 and 160 on June 23 to 25, 155 on June 26 and 27, 150 on June 28, and 155 on June 29 to July 1, then 160, 165 and 160 on July 2 to 4.

Predicted planetary A index is 15, 8, 5, 12 and 10 on May 26 to 30, 5 on May 31 through June 1, then 16, 8, 10 and 8 on June 2 to 5, 5 on June 6 to 15, then 12, 10, 5, 18, 22, 15 and 10 on June 16 to 22, 5 on June 23 to 28, then 16, 8, 10 and 8 on June 29 through July 2, and 5 through the first week of July.

"Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - May 25, 2023

We've seen another seven days of turbulent developments on the Sun and around the Earth.  The large, seen even without binoculars (e.g., eclipse glasses) visible sunspot group AR3310 in the southern hemisphere was the source of the strongest flare on May 16 with an X-ray event maximum of M9.6.

Another group AR3311 in the north, due to its unstable magnetic field configuration "beta-gamma-delta", produced almost all the other flares.  The stronger ones were the cause of Dellinger events (SWF = Shortwave fadeout, in the case of M9.6 it was registered in the whole shortwave range in the region where the Sun was high).

Moreover, the eruptions, combined with sporadic E layer, often significantly affected the propagation in the lower shortwave bands by deep and irregular fadeouts.

SOHO recorded a rare conjunction on May 21, when a filament near the Sun's north pole was ejected as a CME in direction to the Pleiades, Seven Sisters star cluster.  Coronagraph on SOHO has been operating since 1995 and was the first to operate in real time.  No one had ever seen anything like it before.

Since May 24, we observed a new and rapidly growing group of spots, AR3315, in which we can expect more major solar flares as time goes on.  So the turbulent evolution with changing and often worsening shortwave propagation conditions continue.

F. K. Janda, A.R.S. OK1HH"

K7EG wrote:

"I have been in the DX hobby since 1950 and seem to see an increasing, alarming recent trend in solar and geomagnetic activity impacting trends in radio disturbances.  Tell me I am wrong and it's just a 'blip' but solar activity seems beyond the norm and worsening."

I replied that with greater solar activity we should expect more flares, solar wind, and disturbances.  I think the disturbances are normal and expected with the rising solar cycle.

When I suspect conditions are disturbed, this is where I check to see what is happening in real time:

Beautiful aurora:

Sunspot images:

Thanks to NO6ED for this story about an undersea volcano disrupting the ionosphere.

This weekend is the CQ World Wide WPX CW Contest.

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 18 through 24, 2023 were 121, 155, 138, 140, 97, 130, and 153, with a mean of 133.4.  10.7 cm flux was 150.6, 164.6, 169.6, 163.4, 161.5, 154.9, and 164.1, with a mean of 161.2. Estimated planetary A indices were 3, 9, 35, 28, 21, 12, and 12, with a mean of 17.1.  Middle latitude A index was 8, 10, 26, 19, 17, 11, and 10, with a mean of 14.4.



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