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The K7RA Solar Update


This week solar activity fell and then rose again, with average daily sunspot numbers down 23.6 points to 86.1. Average daily solar flux fell from 122 to 107.2. The solar flux on Thursday, July 4 rose to 137.7, the highest since May 16, fifty days earlier.

There was an active geomagnetic day on Saturday, June 29 when planetary A index was 51, high latitude college A index was 73, and mid-latitude A index was 40.

The high geomagnetic activity actually occurred on Friday night on the West Coast, with a planetary A index of 6 at 0300 UTC (Saturday UTC time) and 7 at 0600 UTC. My friend Diana Sorus has been asking me when to go out to see aurora, and I’ve told her to go to a dark place and look north when the K index is high.

I suggested watching and the daily predictions at and to hope for clear skies. The usual problem in the Puget Sound basin of the Pacific Northwest is we have so many overcast days, the chances of seeing aurora are limited. You need just the right combination of high K index (5 or 6 or more), dark skies, and clear weather. Diana wanted to be sure to catch the next one, so she subscribed to a service from which calls or texts her whenever the K index reaches some threshold designated by her.

Last Friday evening she got that call, but unfortunately was too tired from working that day to venture out of the city to watch for aurora. This is unfortunate, because aurora was visible that night in many places, including areas far south of us (aurora is more intense the further away you are from the equator). Skies here have been clear for days, and we had a heat wave over the weekend. I don’t know when she will get that chance again. Could be next week, next month or next solar cycle. I wasn’t watching conditions closely enough to go out and observe for myself.

As you can see at,, and the right combination is rare.

Back on March 1, 2011 the numbers look high enough, but locally the peak activity was during daylight. March 11, 2011 also had a peak at daylight, although the evening hours may have been good also, but March in Seattle tends to be overcast. I tried to find weather records online that would tell me the sky conditions, clear or overcast, but it seems I found everything but that. I did find visibility, which is typically 8-10 miles. An alternative for us is to hop on Interstate 90 and head east 100 miles over the Cascade mountain range to Eastern Washington, where skies are often clear.

The latest prediction (Thursday, July 4) has solar flux relatively high for the next few days, at 140 on July 5-6, 135 on July 7, 140 on July 8-10, then 135, 130 and 120 on July 11-13, 125 on July 14-16, 130 on July 17-19, then 120 and 115 on July 20-21, and 110 on July 22-23. The forecast shows solar flux reaching a minimum of 100 on July 26-27, then another minimum at 95 on August 2, and another peak at 130 on August 13-14.

Predicted planetary A index is 20 on July 5, 15 on July 6, 8 on July 7, 5 on July 8-16, followed by 10 on July 17, 15 on July 18-20, 18 on July 21, and 5 on July 22-26. The geomagnetic indices then show active conditions for the following six days.

OK1HH tells us he predicts geomagnetic conditions as mostly quiet on July 5, quiet to active July 6, quiet to unsettled, July 7, quiet July 8-15, mostly quiet July 16-17, quiet to active July 18-19, active to disturbed July 20, quiet to active July 21, mostly quiet July 22, quiet July 23-24, quiet to unsettled July 25, and quiet to active July 26-27.

At the beginning of the new month, it is now time to look at our 3-month moving average of daily sunspot numbers. The average for the three months centered on May, 2013 (April 1 through June 30) was 106.4, the same as the 3 month average centered on April, 2013 (March 1 through May 31). Actually the two averages were not exactly the same, with the latest 3 months lower by .028. The early period had a sum of 9,792 divided by 92 days, and the latest total was 9,683 divided by 91 days. The daily sunspot number average for June was just 80.2, a drop from 125.6 in May.

The progression of our moving 3-month average for the past year, centered on June 2012 through May 2013 was 96.5, 91.9, 89.9, 81.2, 82.3, 74.4, 82.8, 73.6, 80.7, 85.2, 106.4 and 106.4.

Some radio amateurs have said that perhaps this will be a double-peak solar cycle, like the last one. We don’t know what the rest of the year will bring, but the most recent NASA prediction said the peak of the current cycle would likely be in the summer of 2013, which is now. Remember that exciting period of relatively high activity (at least for this weak solar cycle) in fall 2011? Our 3-month moving averaged peaked in October and November 2011, at 118.8 and 118.6. Now we get two months in a row with 3-month averages higher than any period since the end of 2011, at 106.4 and 106.4. I hope this isn’t as high as it goes.

As we’ve noted during peaks of the previous solar cycles 22 and 23, because the determination of the peak is actually seen using a 12-month moving average, we don’t really know when the peak was until well afterward, perhaps a couple of years out. The long moving average is used to determine the official peak because there is so much day-to-day and month to month variation in sunspot numbers.

An interesting inquiry arrived from Don Prahl, CP4DR/KV7Q:

“I am living in southwestern Bolivia (FG68) high in the Andes Mountains with a station elevation at 4,000 meters (13,000 ft.) I have a very modest station running 100 watts to a vertical on the roof for HF and a roof mounted dipole for 6 meters. The broad side of the dipole is looking north. When I am rag chewing I tell folks I have a very modest station but a tower that is almost 2 1/2 miles high!  While kidding about the elevation of my antenna above sea level is fun, it makes me wonder if a station closer to the ionized layer actually presents any advantage. I have read a lot of articles regarding the advantages of tower height above ground as it pertains to angle of radiation but I have never found any information looking at it just a bit differently. The question would be, with all things being equal (antenna, power output, ionized layer altitude, etc.) would a transmitting signal at 13,000 feet above sea level achieve a longer single path hop than the same station at sea level? If there is an advantage, it would be interesting to see what the ratio of height above sea level to the gain at the receiving end is. Hey, it is tough to breath at this altitude so I need any advantage I can get!

I know that Bolivia is a much needed prize on six meters so I am patiently waiting for that perfect set of conditions so I can confirm CP land to those who are looking. As such, I am really thinking about 50 MHZ. when I pose this question to you.”

Thanks, Don. Sounds like a great location. The only advantage I can think of is that the horizon is more likely to be further away, so lower angles of radiation should be practical. I will cc this to K9LA to see what he thinks. If you are looking down on everything to the north, it seems like it would be great for communicating with North America on VHF.

As always, K9LA gave an excellent and instructive response:

“Go to Click on the "Basic Concepts" link on the left. Then select the article titled The M-Factor.

What you'll see is how the hop distance and the M-Factor (M-Factor = MUF / critical frequency) change versus vertical distance to the ionosphere. This isn't exactly your situation - your situation is with but one end at a different height. But we can use my work to see how much an effect this is.

The difference in hop distance and M-Factor is as follows.

If propagation is via a 5 degree elevation angle to the F2 region at 300 km

Normal hop = 2878 km, M-Factor = 3.25

2.5 miles closer hop = 2855 km, M-Factor = 3.26

If propagation is via a 5 degree elevation angle to the E region at 110 km

Normal hop = 1487 km, M-Factor = 4.94

2.5 miles closer hop = 1448 km, M-Factor = 5.01

The hop length decreases when you are closer to the ionosphere because the wave encounters the ionosphere closer to you. But the M-Factor increases when you are closer because the angle of incidence on the ionosphere is smaller. The effect of being a bit closer to the ionosphere is greatest for the E region.

In summary, the effect of being 2.5 miles closer is certainly there - but it is a pretty small effect. Whether it could be discerned in the real world is questionable.”

Thanks, Carl!

Jon Jones, N0JK wrote on June 28: “Caught a somewhat unusual opening to the Pacific Northwest June 26 on 6 meters from Lawrence, Kansas EM28. I worked N7NW CN87 (Fox Island, Washington), W7EW CN84 (Salem, Oregon) and W7SX CN84 (Elmira, Oregon) around 0335 UTC. N7NW was probably the loudest of the three.”

“This is unusual due to the distance from EM28 to the CN80 grids. It is about 2,500 km. (about 1500 miles). It is a tough distance as it is between the maximum limit for one hop Es (2,300 km) and shorter than the usual range for double hop Es at 3,600-4,400 km. Thus the Pacific Northwest stations are rare on 6 meter Es here in Eastern Kansas. Stations further west like N0LL EM09 (North-Central Kansas) and K0BJ DM99 (Northwest Kansas) work it much more frequently as they are in the usual one Es hop zone. There is a discussion of this here:

Later the same day, Jon wrote: “Some aurora this evening, the first I have worked since fall of 2011. On 6 meters I heard WI9WI, AA9A, KC0CF, WB0RMO/b, a EN26 station on SSB, and K9WKW via Aurora from Lawrence, KS from 0030-0130 UTC June 29.”

“I worked WA9LFO EN54 (who answered my CQ) on 50.098 MHz at 0107 UTC. I was portable with 100 watts and a 2 element Yagi from a nice hill top west of Lawrence overlooking the Kansas River valley to the north.”

“This aurora was not "predicted." It seemed to occur when the Bz went way south the afternoon of the 28th.”

And this week, six meter newcomer Howard Lester, N7SO of Schuylerville, New York (FN33) wrote:

“HEY! It was my first ever 6 meter opening. I made a whole bunch of contacts from 2330-0100 to as far west as Missouri, and as far south as Florida.

On DX Watch at around 2310 Thursday night, July 3 I noticed that a few contacts were being made on 6 meters, so I decided to listen. A newcomer to 6 with my loop antenna at 15 feet, I heard some signals coming through, starting with a W4. Since I have only the little loop for an antenna, and not very high, I didn't expect much for myself. At first, my expectations were confirmed, but in a few minutes I made contact with my first ever "DX" on 6 with two fellows in Knoxville, Tennessee, and got a good report from both. Over the course of the next two hours I worked twelve stations in nine states on both phone and CW, as far west as Des Moines, Iowa, southeast to Knoxville, and south to north Florida - all with good reports. Granted, some or most of the stations I worked have more sizeable antennas, though one was a mobile in northern Illinois, who I worked on July 4 at 0115. He was my final contact for the night.

There seemed to be no pattern, no shifting around of the available propagation; it just "opened up." I could hear Southern stations working up into Ontario and Quebec, and I didn't notice them working anyone to their west. Overall, I sure had a lot of fun.”

And finally, regarding my report last week of my casual Field Day operation as 1C class mobile, it probably didn’t meet the requirements for 1C class. I was able to drive around the cemetery dragging the counterpoise wires, but the screwdriver antenna hanging out the rear passenger window seems a bit much, so it would probably be classed as a portable operation.

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 June 27 through July 3 were 71, 83, 67, 85, 102, 101, and 94, with a mean of 86.1. 10.7 cm flux was 99.5, 101, 100.2, 102.8, 107.8, 114.3, and 124.5, with a mean of 107.2. Estimated planetary A indices were 8, 22, 51, 11, 8, 4, and 4, with a mean of 15.4. Estimated mid-latitude A indices were 8, 20, 40, 11, 10, 5, and 4, with a mean of 14.



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