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The K7RA Solar Update


Unsettled geomagnetic conditions continued this week, punctuated by periods of relative quiet. The most active days were July 14-15. The planetary A index was 20 and 25, and the mid-latitude A index was 15 and 33 on those dates. Of course Alaska’s College A index was higher, at 58 and 34.

The A index is a daily value, and it is calculated from eight measurements per day (once every three hours) of the K index. The K index is a quasi logarithmic value based on magnetometer readings, so each one-point change represents a large difference. The K index is averaged into the daily A index, a linear scale.

This gives a pretty good explanation: Note the graph labeled “The relationship between K and A.”

The planetary A index is based on the planetary K index, which is derived from readings at a network of geomagnetic observatories. The mid-latitude K and A index are from a single magnetometer at Fredericksburg, Virginia, near the intersection of Observatory Road and Magnetic Lane, inside the Fort A.P. Hill Army base, about 8 miles southeast of downtown Fredericksburg, Virginia.

You can sometimes find street names with appropriate references where magnetometers are located, for instance, Geophysical Observatory Road for the magnetometer at Newport, Washington, near 48.27 degrees north, 117.13 degrees west.

Over the past week, the average daily sunspot number declined nearly 33 points to 76.9, while average daily solar flux was down 14 points to 113.9. The average planetary A index barely moved, while the average mid-latitude A index rose two points to 12.9.

But yesterday (Thursday, July 18) the sunspot number jumped to 112, far above the average for the previous seven days.

The latest forecast shows solar flux at 120 on July 19, 125 on July 20-21, 120 on July 22-23, then 115, 110 and 105 on July 24-26, 110 on July 27-28, then 120, 125 and 130 on July 29-31, 135 on August 1-2, then 130, 125, 130 and 135 on August 3-6, 140 on August 7-8, 135 and 120 on August 9-10, 125 on August 11-12, 120 on August 13, and 125 again on August 14-16. It then declines to a minimum of 100 on August 20-21, before rising again.

Predicted planetary A index is 20 on July 19-20, 15 and 10 on July 21-22, 5 on July 23-25, then 30 and 10 on July 25-27, 5 on July 28 through August 3, 10 on August 4-5, 15 and 8 on August 6-7, 5 on August 8-12, 10 on August 13, and 15 on August 14-17.

Petr Kolman, OK1MGW, sends a geomagnetic forecast from the Czech Propagation Interest Group. He says that a growing solar wind “may cause remarkable changes in the magnetosphere and ionosphere on July 19-22 and 25-28.”

He predicts quiet to active geomagnetic conditions on July 19, active to disturbed July 20, quiet to active July 21, quiet to unsettled July 22, quiet July 23-24, quiet to unsettled July 25, quiet to active July 26-27, quiet to unsettled July 28, quiet July 29-31, quiet to unsettled August 1, quiet to active August 2, active to disturbed August 3, quiet August 4, mostly quiet August 5, active to disturbed August 6-7, and quiet to unsettled August 8-10.

At 2330 UTC on July 17 Australia’s IPS Radio and Space Services sent a geomagnetic warning, predicting unsettled to active conditions July 18, active with minor storm periods July 19, and quiet to unsettled conditions July 20.

Just after last week’s bulletin ARLP028 was issued, Bruce Smith, AC4G, of Taft, Tennessee sent in this report: “Just wanted to report a 6 meter sporadic E opening on the morning of July 12 (finally) into EM65 from 0630 AM to 0830 AM CDT just after sun rise. Signals topped out at approximately S-5 with most QSOs made while receiving stations with S-2 signals. The following EU stations were worked or heard by this station during the time range given: EA1EJ, S57RR, G4RRA, CT1HZE, CT1FFU, CT1DIZ, EA5/G0CSC, CT1FJC, PA2M, and the special event station down in the Florida Keys, K4N (EL84). Glad to have made several EU QSOs on 6 meters for the first time this year with my moderate setup using a 5 element Yagi and 100 watts. Still looking for Africa, Asia, and the Pacific.”

Keith Reedy, WA9DRO, of Terre Haute, Indiana reports from last week, “One of my favorite bands is 12 meters. Not much joy on that band lately, just a few openings from time to time state side. However I did hear an Israeli station on 24.964 MHz last Monday evening July 8 at about 8 PM local time. I am using a 3 element beam at about 35 feet. I'm not sure what this means, but I hope more of the same.”

David Moore sent a link to this Los Angeles Times article about the current weak solar cycle:,0,6978639.story

The article presents an interesting observation about weak solar cycles in the early part of any century. Note they corrected a typo in the original article which confused astrology with astronomy. Oh my!

Elwood Downey, WB0OEW, of Tucson, Arizona sent a similar article, about the weak peak:

Pat Hamel, W5THT, of Long Beach, Mississippi wrote on July 15, in an email titled “Frustrating propagation modes”, “The red lines on the maps show it was a super weekend for part of the country on six meters. I have spent part of today (until they packed up), Saturday, and Sunday listening on the K4N six-meter announced frequencies. I am too close to them. I kept getting what sounded like meteor pings.

"This is one of the benefits (?) of living in the middle of the Gulf Coast. If the weather would have been foggy all the way across the gulf, I would have had a pipeline.”

Perhaps he was referring to maps here:

Or here:

Jeff Hartley, N8II, of Shepherdstown, West Virginia wrote on July 15, “E-skip has been down this year compared to normal, but at least the 6 meter Es openings are a bit more frequent with several multi-hop to the west and one to EU/Northern Africa along with another to EA8 only. 15 and 17 seem down quite a bit from June. It has been tough to work the county hunter mobiles on 17 quite often out in the upper Midwest and Montana/Wyoming/Colorado.

"The IARU contest was about as expected with some fun to be had from big PVRC stations operating as NU1AW/3 (IARU HQ) and W1AW/4. I was at NU1AW/3 from N3HBX (signing the /3 was a pain over hundreds of times). But, it was a lot of fun being a multiplier for everyone. 40 opened fairly early to EU with some very strong signals from the big guns in EU and the little guys in the QRN. Northern Europe was weak and watery for the most part but we did log about 4 Asiatic Russians on the west edge in zone 30.

"Seventy-five meter phone was pretty good to Europe with rather poor activity. The HQ stations from Chile and Argentina called in with decent signals. There was enough North American activity to keep us fairly busy thru 0500Z and the Yagi fixed at 300 degrees helped a lot with zone 6. Only one zone 2 (VE6) and one zone 3 (VE4) called in along with VA3RAC and several VE2s and 3s. Most signals were loud enough to be heard easily through the constant S9+ QRN.

"Twenty meters was the 'money band' with very good 1000+ QSO totals from us on phone and the usual 20 meter CW team from DX contests at W3LPL operating 2 interlocked radios picking off QSOs in between CQs as we were doing as well. We had the usual good 20 meter opening around European Russia sunrise and after 0200-0400Z.”

Steve Long, AC6T, of Santa Barbara, California notes, “As an occasional 6 meter fan, I have noticed this past 2 months that the Midwest, East Coast and even Pacific Northwest have enjoyed terrific multihop ES propagation all over the country. Also, frequent openings to Japan and Europe. I'm puzzled (not to mention disappointed) why my corner of DM04 (Santa Barbara) and Southern California in general have had so few decent openings. Six meters has been a great white noise source nearly all summer. Even Arizona seems to do better than we do.  Any wisdom as to why this might be?”

I have no idea, Steve. Happenstance?

Maybe the activity during the CQ Worldwide VHF Contest this weekend will change the 6 meter fortunes of Southern California. See for more information.

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 11 through 17 were 85, 87, 66, 88, 77, 61, and 74, with a mean of 76.9. 10.7 cm flux was 113.4, 117.6, 114, 112.9, 114.1, 113.9, and 111.3, with a mean of 113.9. Estimated planetary A indices were 18, 9, 10, 20, 25, 5, and 5, with a mean of 13.1. Estimated mid-latitude A indices were 15, 9, 8, 15, 33, 5, and 5, with a mean of 12.9.



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