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The K7RA Solar Update


Old Cycle 24 sunspots returned this week, but for only two days (Sunday and Monday) with a sunspot number of 12. Average daily solar flux increased from 66 reported in last week’s bulletin to 67.4 this week.

Radiation from a coronal hole increased the average planetary A index from 5.7 last week to 19.9 this week, with the level on Saturday and Sunday at 38 and 45. In Fairbanks, Alaska’s College A index reached 59 and 86, and at one point on Sunday the K index was 8!

The College K index (a component measured every 3 hours and used to calculate the daily A index) had not previously reached 8 since twice in 2018, on August 26 and two weeks later on September 11.

Predicted solar flux is 68 on September 6-13, 67 on September 14-22, 68 on September 23 through October 6, then 67 on October 7-19 and 68 on October 20.

Predicted planetary A index is 10, 8 and 8 on September 6-8, 5 on September 9-22, 8 on September 23, 5 on September 24-25, then 10, 35, 44, 24 and 8 on September 26-30, 5 on October 1-3, 8 on October 4-5, 5 on October 6-19 and 8 on October 20.

Geomagnetic activity forecast for the period September 06-October 02, 2019 from F.K. Janda, OK1HH.

Geomagnetic field will be:
Quiet on: September 10-11, 15-16, 20 (-21)
Quiet to unsettled on: September 8, 13, 18-19, 22, (25)
Quiet to active on: September (9, 12, 14, 17,) 23-24, 30
Unsettled to active on: September (6-7, 26)
Active to disturbed: September (27-29)

Solar wind will intensify on: September 6, 16-18, (24-27,) 28-30. October 1-2

-Parenthesis means lower probability of activity enhancement.
-The predictability of changes is lower at present.

Lance Collister, W7GJ, of Frenchtown, Montana wrote: "Even though ionospheric propagation (other than Es) seems a distant memory for most of us in northern latitudes, low solar activity means great conditions for 6-meter moonbounce.

“And activity on 6-meter moonbounce has been steadily increasing due to the increased use of the very sensitive digital mode of JT65A and the rapidly expanding 6-meter arrays and amplifiers around the world.

"If you are having trouble keeping track of all the recent activity on 6-meter moonbounce, you are not alone. This has been an amazing year for 6-meter moonbounce DXpeditions. I count 14 new DXCC entities being activated on 6-meter moonbounce this year. In addition to new DXCC opportunities such as ZL7DX and 9K2GS home stations coming on the air this year, there already have been 6-meter moonbounce DXpeditions to V84SAA, T77C, CP1GJ, and CY9C. But be sure to get things ready for even more to come! In the next few months, watch for S79GJ, HB0/S59A, A35JT, VP6R, ZK3A, A21EME, 5H3EME, VP8DBL, and others."

Peter Greene, N2LVI, of Marlton, New Jersey noted that I mistakenly referred to the solar flux measurements at 10.7 GHz, when I should have said 10.7 cm and 2.8 GHz.

Peter sent us a resource for historical solar flux values: He noted: “On a monthly basis, the lowest average since 1947 was in May 1954 (65.36). The most recent low was July 2008 (65.67).”

Jim, WB6BET sent similar historical data.

K3WWP also offered data. But look at his website documenting his long devotion to CW and QRP:

Jeff, N8II, in West Virginia sent what he called a “brief, late report”: “I took part in the Kansas QSO party August 24-25. Propagation on the 24th was definitely near rock bottom. Kansas is a good distance from here for a single F2 hop about 1400-1500 miles to the western border. Starting at 2000Z signals weakened on 20 meters, and by 2100Z activity was quite low. When I returned at 2220Z the band was nearly dead, but I still managed about 6 to 8 more contacts the last with extremely weak signals. And 40-meter signals were also weak until about 2345Z, which is 15 minutes before my sunset. Despite similar SFI, Sunday was much better with good conditions on 20-meters throughout the day. Forty meters was good from 1400-1530Z.

“The mobiles were all easy to hear and work on 20 meters and they were much busier with more callers than Saturday. Fifteen meters appeared to be completely closed to Kansas. I heard and worked KH6LC on 15-meter CW around 1700Z.

“Despite the poor conditions, thanks to good Kansas activity, I managed to work all 105 counties, the last 19 minutes before the end at 1941Z. I also worked all 56 of the active 1x1 special KSQP calls. So, even at the cycle bottom, it is possible to have fun and do well.”


WX6SWW released a new video on September 5:

I will be giving a talk about my history in ham radio (I was licensed at age 12, many years ago), propagation, (and they said I can talk about anything else I want) at the Western Washington DX Club in Seattle on Tuesday, September 10. See for details.

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For more information concerning radio propagation, see 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

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for August 29 through September 4, 2019 were 0, 0, 0, 12, 12, 0, and 0, with a mean of 3.4. 10.7 cm flux was 65.9, 66.5, 66.4, 67.1, 68.8, 68.6, and 68.6, with a mean of 67.4. Estimated planetary A indices were 3, 10, 38, 45, 21, 10, and 12, with a mean of 19.9. Middle latitude A index was 4, 10, 29, 33, 19, 11, and 11, with a mean of 16.7.