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The K7RA Solar Update


A new sunspot group appeared only briefly this week, on August 7-8. It was sunspot 2747, from current Cycle 24. Sunspot numbers on Monday and Tuesday were 11 and 12.

Average daily solar flux shifted only slightly from last week, from 67 to 67.2. Average planetary A index, a geomagnetic indicator aggregated from magnetometers around the world, more than doubled, from 5 to 10.3. This was due to solar wind which raised the planetary A index to 35 on Monday. Alaska’s high latitude college A index reached 61 on Monday and 24 on Tuesday.

Predicted solar flux is 68 on August 9-16 and 67 on August 17 through September 22.

Predicted planetary A index is 5 on August 9, then 8 on August 10-11, 5 on August 12-16, 8 on August 17-18, 5 on August 19-25, 8 on August 26-28, 5 on August 29-30, then 12, 25, 25, 16 and 8 on August 31 through September 4, then 5, 8 and 8 on September 5-7, 5 on September 8-12, 8 on September 13-14, then 5 on September 15-21 and 8 on September 22.

OK1HH sent his geomagnetic activity forecast for the period August 9-September 4, 2019, a day early this week. There will be no forecast from him next week.

Geomagnetic field will be
Quiet on: August 12, 16, 21, September 4
Quiet to unsettled on: August 9, 13-15, 17, 22, 29-30, September 3
Quiet to active on: August 10 (- 11,) 19-20, 23-25, 28, 31
Unsettled to active on: August (18, 26-28), September 1, (-2)
Active to disturbed-none

Solar wind will intensify on: August (9-14,) 27-29, (30-31, September 1-2)

- Parenthesis means lower probability of activity enhancement.
- Next forecast will be issued on August 22

Dr. Tamitha Skov, WX6SWW, posted a new 3-hour-long space weather mini-course a few days ago:

And here is her video report from August 8:

Tamitha will be one of the speakers this Saturday at the Pacific Northwest DX Convention, along with Joe Taylor, K1JT:

Mark, K4SO, in Virginia wrote on August 8: "My friend and neighbor, K1HTV, suggested I drop you a note about a brief, surprising opening on 10 meters this morning.

“I had my small tribander antenna (an A3S) almost due north and decided to drop down from 6 meters to 10 meters, on the way down to more active bands. JTDX was running, as usual, when I got a JTAlert audio message and saw a decode of RV0AR, calling CQ SA. I assumed it was a broken decode of some noise, but in the next cycle it changed to CQ NA! I started calling with 100 W and turned on my Alpha 89 amplifier.

I used JTAlert's text function to encourage him to keep calling, but there was no indication he was online. Luckily for me, his signal continued to build as the amplifier tubes warmed up.”

Mike, KA3JAW, likes to monitor various VHF services, such as FM broadcast, for sporadic-e. He forwarded a report from William Hepburn in Grimsby, Ontario Canada who monitored over 45 minutes of e-skip from 162 MHz weather radio broadcasts from eight stations in Kansas, Arkansas, Colorado and Oklahoma from 2:19 PM to 3:06 PM local time back on July 20. Distances ranged from 839 to 1,253 miles.

If you would like to make a comment or have a tip for our readers, email the author at

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 1 through 7, 2019 were 0, 0, 0, 0, 12, 11, and 0, with a mean of 3.3. 10.7 cm flux was 66.8, 66.9, 65.7, 66.9, 68.1, 68.1, and 68, with a mean of 67.2. Estimated planetary A indices were 8, 4, 3, 4, 35, 12, and 6 with a mean of 10.3. Middle latitude A index was 8, 4, 4, 6, 20, 10, and 6, with a mean of 8.3.




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