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The K7RA Solar Update


Tad Cook, K7RA, Seattle, reports: We saw just one new sunspot group (AR2403) over the August 20-26 reporting week, but it was a big one, directly facing Earth on August 23. Average daily sunspot numbers rose 32.3 points to 69.7, while average daily solar flux increased 28.7 points to 119.7. Another new sunspot appeared on August 27, numbered 2405.

The average daily planetary A index dropped from 21.4 to 14.7, compared with the previous 7 days. The most active days were August 23 and 26, when the planetary A index was 28 and 30, caused by streams of solar wind.

At 0012 UTC on August 27 Australia’s Space Weather Services issued a geomagnetic warning for increased geomagnetic activity on August 27-28 due to a high speed windstream coming from a coronal hole. On August 28 look for active to unsettled geomagnetic conditions.

Predicted solar flux is 110 on August 28-29; 105 on August 30; 100 on August 31; 95 on September 1-3; 100 on September 4-5; 95 on September 6-9; 90, 85, 95, and 100 on September 10-13; 105 on September 14-19; 120 on September 20-21, and 125 on September 22-24. Solar flux values drop below 100 on October 3-9.

Predicted planetary A index is 18, 12, and 8 on August 28-30; 5 on August 31-September 1;  12, 20, 15, 10, and 8 on September 2-6; 5 on September 7-11; 12 on September 12; 15 on September 13-14; 5, 10, 5, 8, and 20 on September 15-19; 28, 20, 12, 18, 12, and 8 on September 20-25, and 5 on September 26-28.

F.K. Janda, OK1HH, sent his weekly geomagnetic forecast. He predicts quiet to active conditions August 28, quiet to unsettled August 29, quiet on August 30, mostly quiet August 31 through September 1, quiet to active September 2, active to disturbed September 3, quiet to unsettled September 4-5, mostly quiet September 6-7, quiet to unsettled September 8-10, quiet to active September 11, active to disturbed September 12, quiet to active September 13, quiet to unsettled September 14, quiet to active September 15-16, mostly quiet September 17, quiet to unsettled September 18, active to disturbed September 19, mostly quiet September 20-21, quiet to active September 22, and active to disturbed September 23.

OK1HH expects increases in solar wind on August 28-29, September 1-5, 10-11, 16-20, (although September 16-17 is less certain), and September 23.

NASA issued a new commentary for the current sunspot cycle, this time with the new V2.0 sunspot numbers, which read higher than the old standard. Historic numbers are also being revised around this new standard.

Using the new numbering system, the maximum of 101 in late 2013 was revised upward from 72, and the peak of 116.4 in April 2014 was increased from 81.9.

The autumnal equinox is on Wednesday, September 23, at 0822 UTC, ushering in the fall DX season.

Dick Bingham, W7WKR, of Stehekin, Washington, sent an interesting link concerning over-the-horizon HF radar operating in Virginia:

Jimmy Mahuron, K9JWJ, in Salem, Indiana, had some observations on daytime regional net operations on 40 and 75 meters.

“40 meters (7.191 MHz) on the RV Service Net was made difficult by the G2 Geomagnetic Storm this morning (August 27), from net time which is 7-9 AM local time (1100-1300 UTC).

“3.74 MHz was much quieter than 7.191 MHz WWV was very light on 10 MHz and not audible at times.

3.74 MHz was relatively quiet at the home QTH but just the reverse for other hams on frequency. The relays on 7.191 MHz made the net possible and if not for the relays would be virtually impossible. Thanks to all on the RV Service Net.”

The geomagnetic storm that Jimmy mentioned produced some visible aurora. See and for reports from the Washington Post weather blog.

David Moore sent another interesting article, this time about coronal heating.

For more information concerning radio propagation, see the ARRL Technical Information. See “What the Numbers Mean, and Propagation Predictions -- a brief introduction to propagation and the major factors affecting it” for an explanation of the numbers used in this bulletin. An archive of past propagation bulletins is on the ARRL website, and the website of Carl, K9LA, offers more good information and tutorials on propagation.

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at and

Click on “Download this file” to download the archive and ignore the security warning about file format. Pop-up blockers may suppress downloads. (I’ve had better luck with Firefox than with IE).

See monthly propagation charts between four US regions and 12 overseas.

Instructions for starting or ending email distribution of ARRL bulletins are on the ARRL website.

Sunspot numbers for August 20 through 26 were 68, 78, 72, 93, 71, 61, and 45, with a mean of 69.7. 10.7 cm flux was 102.8, 110, 116.9, 133.1, 127.7, 121.2, and 126.2, with a mean of 119.7. Estimated planetary A indices were 13, 6, 9, 28, 8, 9, and 30, with a mean of 14.7. Estimated mid-latitude A indices were 11, 6, 8, 23, 7, 8, and 19, with a mean of 11.7.

Send me your reports and observations!




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