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The K7RA Solar Update


We saw some evidence of sporadic-e propagation this week on 6 and 10 meters, always surprising and exciting.

Solar activity was about the same as last week, at least going by the numbers.

Average daily sunspot numbers rose slightly from 68.6 to 74.4, while average daily solar flux only budged from 120 to 120.3.

Geomagnetic indicators were quieter, with average daily planetary A index shifting from 10.7 to 5, and average middle latitude numbers from 9.3 to 4.6. We listed the middle latitude A index on May 6 as 2, but that number is my own estimate. At the end of that day the last K index reading was not reported, and since the A index for the day is calculated from all the K index readings, there was no official middle latitude A index reported, so I came up with my own estimate based on available data.

Thursday's outlook for solar flux is more optimistic than last week's prediction, with no values below 100. Expected flux values are 135 on May 13-16, then 132, 128, 126, and 120 on May 17-20, then 118, 120, 124 and 121 on May 21-24, 118 on May 25-27, 116 on May 28-31, 118 on June 1-5, then 116 and 118 on June 6-7, 120 on June 8-9, 122 on June 10-14, 118 on June 15-17, then 120, 124 and 121 on June 18-20.

Planetary A index is predicted at 8 on May 13, 12 on May 14-15, then 14 and 8 on May 16-17, 5 on May 18-19, then 12 and 8 on May 20-21, 5 on May 22-23, 18 on May 24, 15 on May 25-27, 8 on May 28, and 5 on May 29 through June 15, a nice long quiet spell of geomagnetic stability for more than 2 weeks.

Thursday's forecast was prepared by Trost and Housseal of the U.S. Air Force.

OK1HH wrote: "Solar flares continue to occur, and some of them are throwing several overlapping CMEs into space. The amount of CMEs leaving the sun is large enough to make it difficult to unravel their different shapes and trajectories, which reduces the reliability of predictions. Nevertheless, the geomagnetic activity is mostly low, which can be explained by the fact that the magnetic fields above the solar surface are mostly closed.

"An intense solar flare of class X1.5 was observed on May 10 at 1355 UT in the active region 3006 with a complex magnetic structure. Radiation from the flare ionized the Earth's atmosphere and caused a shortwave radio outage around the Atlantic Ocean, more specifically from Central Europe to the east coast of the United States (see Dellinger effect). Radio transmissions at frequencies below 30 MHz were attenuated for more than an hour after the eruption. 

"Another M-flare on the afternoon of May 11 was a proton flare.

"Another CME on May 11 came from the sunspots on the far side - one just behind the eastern limb of the Sun and the other just behind the western limb. We do not expect the solar wind around the Earth to intensify again."

The Dellinger effect:

Here is a blackout map for the above mentioned May 10 event:

More on this event:

Mystery of the bright spots:

WA6LIE wrote in a message titled "TEP to Fiji": "Yesterday evening March 10 just after 0600 UTC I was getting ready to go to bed and saw 3D2AG calling CQ on 6 meter FT8. I gave him a call and we made a QSO.

"He was decoded here in Salinas, California. CM96 for an hour and a half with no takers. Looks like the Magic band is starting to play!

"I will go back to my saying: Gotta be in the right place at the right
time and get lucky!  Heads up!"

K5JRN wrote: "Today (05/07/2022) at 1601 UTC, I caught a brief 2-meter E-skip opening and worked W4AS in EL95, using FT8, 25 Watts, and an indoor mobile whip antenna. It was an 1100-mile hop from EM10, in Austin, TX, to the Miami, FL area. He was +04 here and I was -24 there, no doubt because of my low power and cross-polarization. It was a new grid for me on 2, and I'm happy to have it."

A massive solar flare, almost:

Solar cycle progress update from NOAA:

Real time geomagnetic updates:

The latest Space Weather from Dr. Skov, WX6SWW:

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 5 through 11, 2022 were 85, 64, 66, 89, 71, 62, and 84, with a mean of 74.4. 10.7 cm flux was 119.9, 119.2, 118.1, 119.2, 117, 115.8, and 132.9, with a mean of 120.3. Estimated planetary A indices were 4, 5, 3, 6, 8, 3, and 6, with a mean of 5. Middle latitude A index was 4, 2, 4, 7, 8, 2, and 5, with a mean of 4.6.




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