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The K7RA Solar Update


The average daily sunspot numbers were up nine points to 25.3 for this week, compared to the May 20-26 period; the average daily planetary A index rose nearly 10 points to 14.3, and this rise in geomagnetic instability came with the increase in solar activity. Sunspot numbers for May 27-June 2 were 11, 12, 43, 40, 39, 14 and 18, with a mean of 25.3. The 10.7 cm flux was 72.7, 73.2, 73.7, 73, 72, 72.7 and 74, with a mean of 73. The estimated planetary A indices were 4, 10, 33, 19, 16, 12 and 6, with a mean of 14.3. The estimated mid-latitude A indices were 1, 7, 15, 14, 14, 9 and 4, with a mean of 9.1. The monthly averages of daily sunspot numbers for 2010 are 21.3, 31, 25.2, 11.2 and 20.

Sunspot group 1072 -- reported in last week’s bulletin -- was visible for nine days, until May 28. When it was gone on May 29, three new groups appeared: 1073, 1074 and 1075. On May 29-31, the daily sunspot numbers were 43, 40 and 39, but geomagnetic indices were high as well, with the planetary A index at 33 on May 29, and planetary K index up to 5. On the same day, the college A index (Alaska) was 53, with college K index as high as 7.

On May 31, group 1074 was gone and it was the last day that groups 1073 and 1075 were still visible. On that day, new group 1076 appeared, and through June 3, the total area (in millionths of a solar hemisphere) was 20, 20, 40 and 190. The increase from June 2 to June 3 was big (up 375 percent), but curiously, the sunspot number for those dates declined slightly, from 18 to 17, while the solar flux rose from 74 to 74.6.

The prediction from USAF and NOAA has solar flux slowly declining in the short term, from 75 for June 4, to 74 on June 5-6, 73 June 7-9, 72 on June 10 and 70 on June 11-17, then rising to a peak of 82 on June 28.The predicted planetary A index for the next seven days -- June 4-10 -- is 10, 8, 5, 8, 8, 5 and 5. Geophysical Institute Prague predicts quiet conditions June 4, quiet to active June 5-6, quiet to unsettled June 7-8 and quiet again on June 9-10. Some may have noticed that NOAA showed a solar flux value of 0 for June 2, which is impossible. I don’t know how that was left out, but you can always get the data from the source that shows a solar flux value of 74.6 for that day.

ARRL Field Day is June 26-27, coinciding with what may be the next short term peak in solar activity, according to the NOAA and USAF prediction; they are calling for solar flux values for June 25-28 at 80, 80, 80 and 82.

Field Day 2009 was spotless. In fact, there were no sunspots at all from June 25-July 2, 2009. Suppose that there are sustained daily sunspot numbers around 25 for the days leading up to Field Day 2010? What differences could we expect?

Checking W6ELprop from Southern California to Ohio, for example, shows very little difference, except on 15 meters there is a much greater chance for an opening. Both show 40 meters opening up after 0000, reaching optimum signal strength 0330-1030. Both show 20 meters open through the day, but weakest periods around 1330-1430 and 2300-0000 and strongest signals through the night, 0100-1200.

We see similar results from Atlanta to the center of the continental United States, somewhere in Kansas. The path is quite a bit shorter, and we see 20 meters opening a half hour earlier than last year, at 1500 and lasting until 2130, a half hour later than last year.

A similar test from Hawaii to the mainland shows a big improvement over last year, especially on higher frequencies, such as 15 meters. In Field Day, there is no bonus for DX, and it isn’t like ARRL Sweepstakes where multipliers are earned for each new Section worked, so the only incentive is to work as many stations as possible. But for a Field Day station in Hawaii, the increased solar activity will make a big difference in the number of stations they can work.

Now at the beginning of a new month, we can look at our quarterly moving averages for sunspot numbers. We use a sliding three month window for averaging the data, so the latest number is for March 1-May 31 and centers on April. For May 2009-April 2010, the three month averages are 4.2, 5.2, 4, 4, 4.6, 7.1, 10.2, 15.2, 22.4, 25.7, 22.3 and 18.5. You can see that the numbers have declined a bit. The monthly averages of daily sunspot numbers for 2010 are 21.3, 31, 25.2, 11.2 and 20.

Floyd Chowning, K5LA, and David Clark, K5PHF, both in DM61 in El Paso, Texas, and George Olcott, K7ICW, in Las Cruces, New Mexico (DM62) all worked Ron McGaha, K7MAC, in Nampa, Idaho (DN13) on June 2 at 1758 on 2 meter SSB. This rare sporadic-E opening lasted 30 minutes. The distance from K5LA to K7MAC is 973 miles, according to my calculations. If you check here for K5LA, you will see some detail on his propagation beacons on 30, 17, 10 and 6 meters, and his participation in

David Greer, N4KZ of Frankfort, Kentucky wrote a detailed description of his 2 meter sporadic-E adventure. “It’s June, so it must be time for the VHF bands to start rockin’. They did not disappoint on June 3, with 6 meters providing 3 dozen SSB and CW QSOs from central Kentucky (EM78) to the West Coast. Of course, the day before wasn’t shabby either, with a dozen contacts into W1 and the Caribbean.

“But it was June 3 that provided some memorable QSOs. In the midst of handling a pile-up of West Coast callers, I got a call from KD5CCG in Arkansas. That got my attention because it showed the E-skip distance was shortening up -- often a tip-off that E-skip will show up on 2 meters. So I set my rig and amp on 144.200 MHz and called several CQs while beaming west. Nothing, zilch. So I turned on the squelch and went back to to 6 meters.

At 0047, N0YK came on the 2-meter frequency with an S9 plus SSB signal calling CQ. I answered him and we both logged 59 reports. He’s in Kansas, DM98. That’s western Kansas, almost to the Colorado line. Exactly 10 minutes later, WB2FKO (DM65) in New Mexico came roaring in with a strong ‘CQ 2 meter E-skip, Beaming east.’ Bingo, he was in my log too, but not before I nervously asked him to repeat his call twice. Even after 41 years of ham radio, such a contact gives me chills. My logging program shows 1173 miles between our locations. I've been on and off 2 meter SSB since 1975 and it was only the second time I had worked New Mexico from Kentucky. Wow, nearly 1200 miles on 2 meters!

“At 0106, I worked N0QKY -- also in Kansas -- and then made a quick QSO a minute later with KA0RID, another Kansas station. It’s about 600 miles from my location to central Kansas and those are great 2 meter contacts, but the nearly 1200 mile QSO with New Mexico was really special. During the opening, I copied, but did not work, K7ICW in New Mexico and N0POH in Colorado. At that point, things were quite busy on 144.200 MHz with QSOs, CQs and QRZs galore. I do wish guys would spread out a bit more during these openings!

More than 30 minutes after I first heard and worked N0YK, I was still copying him, but the signals were in the noise as the 2 meter E-skip opening was fading. I have modest stations on both bands. I run 200 W out and a 9-element M2 Yagi at 60 feet on 2 meters and 100 W out to a 4-element Yagi at 55 feet on 6. Antennas are important, but time and time again it’s proven that much of the battle at VHF is about being in the right place at the right time.”

Thanks, Dave!

All times listed are UTC, unless otherwise noted.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. You can find a guide to articles and programs concerning propagation here. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail at




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