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The K7RA Solar Update

05/14/2021

Tad Cook, K7RA, Seattle, reports: Sunspot activity returned last Friday, May 7, and has held steady since. Average daily sunspot numbers rose from 11.9 to 21.1, and average daily solar flux was up 2.1 points to 74.3 for the reporting week ending May 12.

Geomagnetic activity was quiet until Wednesday, May 12, when the planetary A index went to 41 as the result of a coronal mass ejection (CME) that blasted out of the sun on May 9. It was not expected to be very strong, but when it struck on May 12, it sparked a G3 class geomagnetic storm — the strongest in the current solar cycle.

The planetary A index rose to 41, far above an average of 3.8 on the previous 6 days. The average daily planetary A index for the May 6 – 12 reporting week was 9.1 and average middle – latitude A index was 7.4.

Predicted solar flux over the next month is 75 on May 14 – 19; 70 on May 20 – 21; 72, 80, and 79 on May 22 – 24; 78, 77, and 73 on May 25 – 27; 72 on May 28 – 30; 70 on May 31 and June 1; 71 and 75 on June 2 – 3; 76 on June 4 – 5; 74 on June 6 – 7; 75 on June 8 – 9; 77 on June 10, and 79 on June 11 – 13.

The predicted solar flux of 84 on June 15 in the 45-day forecast seems to be an outlier. It’s odd that predicted solar flux would shift from 78 to 84 to 77, but we saw a similar prediction recently for that same value a week into the future. Any trace of it here seems to have disappeared down the memory hole.

Predicted planetary A index is 5 on May 14 – 16; 15, 12, 8, 5, and 8 on May 17 – 21; 5 on May 22 – June 5; 8, 5, and 8 on June 6 – 8, and 8, 5, 12, 18, and 15 and on June 9 – 13.

Here’s the geomagnetic activity forecast for May 14 – June 8 from F.K. Janda, OK1HH, of the Czech Propagation Interest Group, which has been compiling weekly geomagnetic activity forecasts since January 1978.

The geomagnetic field will be:

  • quiet on: May 19, 25-26, (27-31)

  • quiet to unsettled on: May 21, 24, 31, June 1-8

  • quiet to active on: May (14-16, 18, 20-23)

  • unsettled to active: May (17)

  • active to disturbed: none

  • Solar wind will intensify on: May (16,) 17-18, (21-25,) 28-30

Remarks:

- Parenthesis means lower probability of activity enhancement.

- Contradictory indications significantly reduce forecast accuracy.

Jon Jones, N0JK (EM28), wrote: “6-meter E skip to W6 on May 14 to Silicon Valley. Worked AH0U and N5KO, both in CM97. They are in the sporadic E ‘doughnut’ between single and double hop Es.”

Ken Brown, N4SO, checks this graph of the EISN — the estimated international sunspot number — a daily value obtained by a simple average over available sunspot counts from 85 world-wide observers in the SILSO network and, “compares it with propagation on 30 and 17 meters. Of interest are stations in China, Japan, Korea, and Asiatic Russia propagated at 6,000 miles plus.” Also see the SIDC/SILSO International Sunspot Number.

Ken also reported that on May 11, the W1AW code practice bulletin on 17 meters were 40 dB over S-9. “So I called CQ QRP.” He had the power set all the way down on his Elecraft K2, which is 100 mW. He heard or worked W3UA, KM3T, and at 3 W worked K7QO. On FT8 on 30 meters, he worked “a long string of Japanese stations” from 0745 until 1114 UTC — 26 stations in all. The strongest were JE0ART (–3 dB) and JA1IOA (+5 dB) over a roughly 7,000-mile path.

The Reverse Beacon Network (RBN) on 10 meters showed KC0VKN (Iowa) in QSO with K4SE (Tennessee) at 1043 UTC on May 11.

This article, “Using Sporadic E, Es Propagation for Amateur Radio” in Electronics Notes, was mentioned in The ARRL Contest Update newsletter for May12. Then visit the propquest page for an interesting online real-time sporadic-e tool.

Here are two recent reports [1] [2] from Space Weather Woman Tamitha Skov, WX6SWW.

Sunspot numbers for May 6 – 12 were 0, 15, 17, 18, 36, 31 and 31, with a mean of 21.1. The 10.7-centimeter flux was 70.8, 74.5, 71.6, 75.9, 76.5, 76.1, and 74.7, with a mean of 74.3. Estimated planetary A indices were 4, 3, 3, 4, 6, 3, and 41, with a mean of 9.1. Middle latitude A index was 2, 3, 4, 6, 8, 4, and 25, with a mean of 7.4.

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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