The K7RA Solar Update


Average daily sunspot numbers rose this reporting week (June 15-21) from 4.9 to 29.4. The previous week had four days with no sunspots, and this week there were no zero sunspot days, hence the dramatic increase in the average.

Average daily solar flux barely budged from 74.4 to 74.6

Average daily planetary A index went from 7.3 to 9.4, and mid-latitude A index from 6.9 to 8.1.

Predicted solar flux is 75 on June 23-28, 74 on June 29 through July 4, 75 on July 5-7, 77 on July 8-9, 74 on July 10-14, 75 on July 15-17, then 74, 72 and 74 on July 18-20, 70 on July 21-23, 74 on July 24-31, 75 on August 1-3 and 77 on August 4-5.

Predicted planetary A index is 12 on Jun 23-24, then 10 and 8 on June 25-26, 5 on June 27 through July 12, then 20 and 12 on July 13-14, 10 on July 15-16, 5 on July 17-18, 8 on July 19, 12 on July 20-21, then 10 and 8 on July 22-23, then 5 on July 24 through August 6.

Geomagnetic activity forecast for the period June 23-July 18, 2017 from F.K. Janda, OK1HH.

“Geomagnetic field will be:
Quiet on June 27, July 4-5
Mostly quiet on June 28-29, July 1, 3, 7, 17
Quiet to unsettled June 26, July 2, 6, 12, 18
Quiet to active on June 25, 30, July 9-11, 15
Active to disturbed on June (23-24,) July (8,) 13-14, 16

Amplifications of the solar wind from coronal holes are expected on June (26-27), July (8,) 9-17, (18).

– Parenthesis means lower probability of activity enhancement and/or lower reliability of prediction.

F. K. Janda, OK1HH”

This weekend is ARRL Field Day. Conditions should be good. Earlier forecasts had the planetary A index this weekend at 5, but currently for Saturday and Sunday it is 12 and 10, which is certainly workable. Predicted solar flux is 75 for both days, better than recent predictions for June 24-25.

Here is a 6 meter report from George Hall, N2CG: “On Father’s Day 2017 there was an Es opening from the US East Coast to the Caribbean and Northern South America region that began around 2145Z, according to spots on the DX spotting websites, and it lasted for about two hours.

“I was returning home (Northern New Jersey, grid FN20wv) after having Father’s Day dinner with my wife and arrived around 7 PM EDT/2300Z. Soon after, I got on 6 meters and heard YV50ARV/6 in FJ78 on 50.125 MHz SSB coming in 59+ and soon had him in my log. Over the next 45 minutes I worked the following exchanging 59/599 signal reports both ways: YV5IUA in FK60 on SSB; PV8ADI in FJ92 on CW; KP4JRS in FK68 on CW; WP2B in FK77 on CW; and KP4EIT in FK68 on SSB.

“Looking at the DX spots being posted during this opening, I counted about 80 percent JT digital mode spots vs 20 percent SSB/CW mode spots. Last year during a typical 6-meter Es opening this was the exact opposite with about 80 percent SSB/CW spots vs 20 percent JT digital mode spots being reported.

“So it looks like the JT digital modes have made a very strong and dominant role on working 6 meter DX and in such a short period. If the JT digital modes can evolve with faster turnaround times (like what was recently reported on the WSJT-X reflector); then we may see 6-meter DX activity become almost exclusively fast turnaround JT digital modes.”

Interesting article about sunspots, and how they are observed:

Dr. Tamitha Skov mentions Field Day:

Another solar article:

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 June 15 through 21, 2017 were 28, 28, 28, 27, 26, 34, and 35, with a mean of 29.4. 10.7 cm flux was 77.4, 73.5, 74.8, 74.9, 73.6, 74.4, and 73.7, with a mean of 74.6. Estimated planetary A indices were 4, 25, 15, 10, 5, 3, and 4, with a mean of 9.4. Estimated mid-latitude A indices were 5, 18, 12, 9, 7, 3, and 3, with a mean of 8.1.

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