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The K7RA Solar Update


All solar indices rose over the past week, and geomagnetic indicators were lower.

Average daily solar flux rose from the previous seven days at 52.6 to 58.1, and average daily sunspot numbers rose from 91.6 to 103.6.

Average daily planetary A index went from 15.7 to 10.6 and average daily mid-latitude A index changed from 14.1 to 11.1.

The latest (Thursday night) predictions for solar flux show 100 on July 22-23, 95 and 90 on July 24-25, 85 on July 26-27, 80 and 75 on July 28-29, 70 on July 30 to August 4, 80 and 95 on August 5-6, 105 on August 7-16, 100 on August 17-18, then 95, 90, 80 and 75 on August 19-22, and 70 on August 23-31. For the next few days following the end of August the prediction shows a sharp rise in solar flux from 70 to 105.

Predicted planetary A index levels are at 10, 8, 12, 8 and 5 on July 22-26, 8 on July 27-31, 5 on August 1-2, 20 on August 3-4, 15 on August 5, 10 on August 6-7, then 20, 8, 12, 10 and 8 on August 8-12, 5 on August 13-14, then 8, 12 and 15 on August 15-17, 10 on August 18-19, 8 on August 20, 5 on August 21-23, then 8 and 9 on August 24-25, 8 on August 26-27, 5 on August 28-29, and 20 on August 30-31.

At 2341 UTC on July 19 the Australian Space Forecast Centre issued a geomagnetic disturbance warning:

A shock wave signature was detected in the solar wind on 19 July at 2300 UTC. A geomagnetic sudden impulse is expected, followed by increased geomagnetic activity up to minor storm levels.


20 Jul:  Active to Minor Storm
21 Jul:  Active
22 Jul:  Unsettled to Active

The Geomagnetic activity forecast for the period July 22 to August 16, 2016 from OK1HH follows.

Geomagnetic field will be:
Quiet on August 1, 13-14
Mostly quiet on July 25, 28-29, August 11-12
Quiet to unsettled on July 26, August 7, 16
Quiet to active on July 22, 27, 30-31, August 2, 5-6, 8-9, 10, 15
Active to disturbed on July 23 or 24, August 3-4

Increased solar wind from coronal holes is expected on July 27-28, July 30 through August 2, and August 7-8.

Bob Sherman, K2SJP, of Lutz, Florida noted a 10 meter opening on July 11 when he worked many West Coast stations.  The next day on 10 meters he worked a station in Kuwait.

Dave Grubbs, N4EF, of Apopka, Florida wrote, “You wrote in Propagation Forecast Bulletin #29 that any perking up of propagation would be unpredictable and temporary -- how right you were.

“There was a fleeting 30-minute nighttime opening from my central Florida home on 30 meters on July 17. The band was dead at 0745 UTC (3:45 AM EDT) and there were no replies to my CQs on 10112 kHz.  About 15 minutes later, I copied a GI4 station, JA1KIH, and CO8LY at the same time within 500 Hz of each other.

“The GI4 was engaged in a QSO and the JA1 and CO8 were calling CQ simultaneously nearly on top of each other. I worked Taka, JA1KIH, with a 559 report each way which was thrilling since I was running 100 watts to a dipole 15 feet high in my attic. The Cuban station was loud enough to cause interference to my conversation, yet Eduardo is only 700 miles (1113 km) from me and had a steady signal. Was this a very short sky wave hop or a long groundwave signal from Cuba?

“My Florida location and Taka's station appear to be in the gray line at the same time, but this brief opening occurred at 0800 UTC, which was 2 hours 39 minutes before my sunrise and hence not attributable to terminator/gray line propagation.  The band was void of CW again until well past sunrise.”

Check out Dave’s interesting post and images on his call sign listing on

Actually what I was trying to say in last week’s bulletin was any increase in solar activity would be temporary.

Ted Leaf, K6HI, in Kona, Hawaii asked “What is the correlation between sunspot numbers and solar flux?”

There is a high correlation between sunspot numbers and solar flux, assuming you are looking at smoothed values for each. Smoothed sunspot numbers average a year of data, so the actual value lags behind the latest data by six months.

Here is an article by K9LA on the topic:

Determining the sunspot number is somewhat subjective, and it is also tough to do when the sky is overcast. But the 10.7 cm solar flux is completely objective. It involves pointing a parabolic dish at the sun at local noon, then measuring the radiation at 2.8 GHz.

This paper notes a correlation which also incorporates solar irradiance:

Interesting article about our sun in a recent issue of The Atlantic:

Jeff, N8II, in West Virginia reported on July 16:

“Some of your readers should have experienced 2-meter Es on Friday evening (July 15) around 0000-0100Z. showed estimated MUFs as high as 180 MHz over grids in eastern OH, NW PA, and western NY. I worked as close as EN91 on 6 meter and many stations centered around Chicago extending eastward including IN and OH both in EM79. NP4A was also worked and the evening before I logged 3 or 4 Puerto Rico hams on 6 meter phone and CW, all in FK68.

“Despite the improved SFI, 15 meters remains dead, but I have not had time to listen much since the IARU contest last Saturday July 9 when EU signals were mostly weak and from south EU, but I did work around 50 of them along with some Es into New England and quite a few Caribbean and SA stations.”

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of the 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 July 14 through 20 were 54, 73, 47, 51, 68, 58, and 56, with a mean of 58.1. 10.7 cm flux was 95.1, 102.1, 106.6, 105.2, 107.1, 100.8, and 108, with a mean of 103.6. Estimated planetary A indices were 12, 11, 8, 6, 4, 10, and 23, with a mean of 10.6. Estimated mid-latitude A indices were 16, 10, 8, 10, 4, 11, and 19 with a mean of 11.1.



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