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The K7RA Solar Update


Tad Cook, K7RA, Seattle, reports: Sunspots have continued to appear every day after April 11 — the last day with no sunspots.

Average daily sunspot number rose this week from 35.1 to 47.6, and average daily solar flux also rose, from 78 to 79.2.

Geomagnetic indicators were quieter, with average daily planetary A index declining from 16.4 to 10.7. The most active day was April 25 with a planetary A index of 20.

Predicted solar flux over the next month is 77, 75, and 72 on April 30 – May 2; 70 on May 3 – 6; 72 on May 7 – 9; 73 on May 10 – 11; 74 on May 12 – 13; 77 on May 14; 79 on May 15 – 23; 78 on May 24 – 2, and 75 and 73 on May 28 – 29.

Predicted planetary A index 8 on April 30 – May 1; 15, 12, 12, and 8 on May 2 – 5; 5 on May 6 – 10; 8, 12, 20, and 30 on May 11 – 14; 15 on May 15 – 16; 12 on May 17; 5 on May 18 – 19; 15 and 10 on May 20 – 21; 5 on May 22 – 28, and 15, 12, and 10 on May 29 – 31. After that, things are quiet over the first week of June.

Here’s the geomagnetic activity forecast for April 30 – May 25 from F.K. Janda, OK1HH. The geomagnetic field will be:

  • quiet on May 18 – 19, 25

  • quiet to unsettled on May 5 – 11, 17, 24

  • quiet to active on April 30, May 12, 20 – 23

  • unsettled to active May (1 – 4,) 16

  • active to disturbed May 13 – 14, (15)

  • Solar wind will intensify on (April 30 – May 1),

May 3 – 5, (6 – 7, 10 – 11, 16,) 17 – 18, (21 – 25)


* Parenthesis means lower probability of activity enhancement.

* Contradictory indications significantly reduce the accuracy of the forecast.

Jon, N0JK, in Kansas, reports:

“On April 26 @ 2100z I copied LU2FFD (FF97) on 50.313 MHz FT8 at –11 dB. Did not complete a contact. This was a sporadic E to TEP path."

Update from Frank, W3LPL:

“Propagation is somewhat better, but at times somewhat worse, as Solar Cycle 25 somewhat fitfully climbs toward solar maximum, likely in late 2024. Slowly improving propagation interrupted by more frequent and intense geomagnetic storms are both encouraging indicators that Solar Cycle 25 is starting to accelerate to solar maximum likely in late 2024.

“The recent sustained rise in SFI is a positive indicator that Solar Cycle 25 is finally starting to accelerate and gradually improve propagation on the higher bands. So far the improvement is minor, but the recent sustained increased SFI is good news and an indicator of likely significant improvement during the night on 20 and 30 meters this summer and generally improved propagation on 30 meters and above by the October/November contests.

The solar flux adjusted for the varying distance between the earth and the sun, has been mostly in the high 70s and low 80s since mid-April. This slowly rising trend is likely to continue, and we’re likely to see adjusted SFI sustaining in the low to mid 80s or even higher by this summer.

“The other good news — yes, good news — is that coronal mass ejections (CMEs) are now occurring much more frequently. More frequent CMEs are a reliable indicator of accelerating Solar Cycle 25 progress. Fortunately, CMEs significantly degrade propagation only when two conditions are met simultaneously: (1) the CME is earth directed, and (2) the orientation of the north-south component of the interplanetary magnetic field is southwards (–Bz).

“By now, May QST has arrived in everyone’s mailbox. Because NASA now forecasts solar maximum in 2024, you may want to get out the red pencil and revise the four occurrences of ‘2025’ in my article to ‘2024.’”

WB8VLC reported from Salem, Oregon, on April 24:

“Another 10 meter good day. Today 10 is open again on both SSB to South America (Chile) and CW to New Zealand, with great signals even though the solar numbers are nothing to brag about.

“A quick listing of today’s openings up to this time and the band is still open but I’m just listening now.

“Two contacts are fine for me today, as I don’t like being a DX Piggy and I’d rather listen and let others have at it while I do some radio programming on some new 6 meter FM land mobile radios, and while I’m listening now the band is still going long to ZL on CW, and Chile on SSB:”





SSB FE36fu Chile





CW RF80lf New Zealand

Earlier he reported:

“This is a small report what with me only having a couple of hours of time to get on the radio these days on weekends and week-day real work-work and these are stations that I worked during my breaks.

“April 22 on 10-meter FT8 was interesting, with a nice opening to Indonesia on 28.074.

“Even though it’s FT8, the Indonesians were audible, with tones actually moving my K3’S S-meter to around 5/5.

“April 20 was a great day with activity on 29.6 FM to New Mexico and Brazil using my cross-coupled 10 FM to 220 remote base while at work during breaks.

“The weekend of April 18 was typical of what I experience every weekend, SSB and CW to South America with strong sigs for hours.

“My setup is a K3S with homebrew LDMOS amp at ~300 W on SSB/CW into a 4el OWA Yagi at 30 feet.

“For 29.6 FM, I use a Motorola Maxtrac with 60 W out that is cross-connected to a 220 MHZ Maxtrac set up as a remote base system, so I can operate 10 FM from work during lunch time, and I use the same 4-element OWA Yagi as I use on SSB/CW when operating FM:”











































Here’s an article from Oxford Academic on forecasting Solar Cycle 25

Ted Leaf, K6HI, sent this EarthSky article about a flare in another solar system.

Sunspot numbers for April 22 – 28 were 42, 29, 62, 57, 54, 47 and 42, with a mean of 47.6. The 10.7-centimeter flux was 83.5, 77.4, 78.5, 78.8, 80.3, 79.4, and 76.8, with a mean of 79.2. Estimated planetary A indices were 5, 15, 10, 20, 14, 8, and 3, with a mean of 10.7. Middle latitude A index was 4, 15, 10, 16, 12, 8, and 4, with a mean of 9.9.

For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check out K9LA’s Propagation Page.

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

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

Share your reports and observations. 



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