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The K7RA Solar Update


This was a very active week for solar flares and aurora. On Monday and Tuesday the planetary A index was 55 and 76, indicating a geomagnetic storm. The planetary A index was high again on Thursday, June 25 at 33, and the high latitude college A index was 42.

It turns out that the magnetometer at Fredericksburg, Virginia was knocked out on five of the seven days, so the mid-latitude A index we are reporting for June 18-21 and June 24 are approximations, or actually wild guesses based on other readings from magnetometers that were working.

Average daily sunspot numbers dropped from 99.9 during the week of June 11-17 to 71.6 a week later. Average daily solar flux declined from 135.9 to 130.8. Average daily planetary A index rose from 12.1 to 24.4.

The current outlook from NOAA/USAF has solar flux at 100 on June 26-27, 105 on June 28, 110 on June 29, 115 on June 30, 120 on July 1, 125 on July 2-4, 120 on July 5-6, 125 on July 7-10, 130 on July 11-20, 125 on July 21-22 and 130 on July 23-24.

Predicted planetary A index is 15 and 45 on June 26-27, then 60, 18 and 8 on June 28-30, 5 on July 1-4, then 25, 15 and 12 on July 5-7, then 10, 5 and 8 on July 8-10, 18, 12 and 8 on July 11-13, 5 on July 14-17, 8 on July 18-19, 5 on July 20-31, then 25, 15, 12 and 10 on August 1-4.

Petr Kolman, OK1MGW, believes the geomagnetic field will be quiet to active on June 26-27, mostly quiet June 28-30, quiet July 1-2, quiet to unsettled July 3, active to disturbed July 4, quiet to active July 5, quiet to unsettled July 6-8, mostly quiet July 9-10, quiet to active July 11-12, quiet to unsettled July 13-14, mostly quiet July 15-17, quiet to unsettled July 18, and quiet to active July 19-22.

Rich Zwirko, K1HTV, reported on June 21: “Here in the Mid-Atlantic at K1HTV in Amissville, VA, the Magic Band came alive just before 1600Z on Father’s Day, June 21. The first of 13 countries that I worked were all from a southerly direction. NP3CW was first in the log, followed by Yuri, UT1FG/MM in EL59 off the Cuban coast, CO3JA, 6Y5WJ, YV4NN and XE2CQ in DM12 northwestern Mexico.

“From 1650Z to 1750Z I worked 17 stations in W6 and W7 land. During that same hour, stations from GA and FL to as far west as NM and XE2 were working into HA, S5, YT, IS0, 9A and DL, but all I heard to the east during that hour was F2DX calling XE2X.

“It wasn't until 1845Z that I heard European DX here. In the next 65 minutes I worked I0JX, IK5MEJ, IZ5BRW & IK5PWJ, HA8CE, ON7BG, OK1DO, G4DBL, S59A, HA8FK, PA2M and ON4IQ.  That was it for DX to the east for the day.

“Local late afternoon to early evening produced many more double hop QSOs to the West Coast, 15 stations in AZ, 15 in CA, 3 in NM and 1 in NV. It was a memorable Father’s Day.”

Jon Jones, N0JK, wrote: “I worked Father's Day, but got off a little early at 2100Z and worked WU1ITU on 6 meters before going home.

“Sunday evening I worked 6Y5WJ from home for a 'new one' on 6 so all in all not a bad day.

“I have a shoe box full of 6 meter JA cards.”

Rich Zwirko, K1HTV wrote again: “After the excellent double hop 6 meter Es earlier in the June 22 UTC day, the 6 meter and 2 meter bands came alive with aurora propagation around 1940Z. After making a few 6 meter AU QSOs to W1 & W2 land, I switched to 144 MHz at 1945Z. I quickly worked K9CT in IL (EN50), W9EWZ in WI (EN52), WB8AIZ in MI (EN82) on 2 Meters as well as a couple of closer stations before the buzz mode switched off. On June 23, 6 meters was alive with Es propagation when I got on around 0100Z. I worked dozens of stations in the Midwestern States via Es until around 0340Z, when the aurora returned. It only lasted for about 30 minutes. I worked a few VE3s on 6 meters before switching to 2 meters to work stations in Maine, PA and Ohio.

“Later that same UTC day (June 23) the 6 meter band was alive with single and double hop E-skip propagation. From 2130Z until the end of the UTC day, I worked what seemed to be an endless stream of over 120 stations, with over three dozen from W6 and W7 land.

“Shortly after 0000Z on June 24, while watching the DXMAPS.COM web site, it indicated that a patch of ionization, with an MUF in excess of 150 MHz, was well positioned for possible 2 Meter propagation. It appeared to favor an area to the southwest of my FM18 VA QTH around 1000 to 1100 miles away. At 0006Z, W5VQ in EM13 (TX) answered my 2 Meter SSB CQ. At 0028Z I called and worked K7XC in EM12, also in Texas, on CW, then again a few minutes later on SSB. Both Texas stations were around 1100 miles away. At 0028Z I was called on SSB by N5NET in EM26 in Oklahoma. I also heard but didn't work Sam, K5SW in EM25. About 15 minutes later the same patch apparently was responsible for a QSO between W0LD operating temporarily in FM05or (NC) and K5PHF in DM61ts (TX), a distance of 1550 miles.

“The evening produced a number of ionized patches in the center of the country and others farther west, making for many hours of exciting VHF propagation.”

Elwood Downey, WB0OEW, wrote to Ken Tapping of the Penticton observatory in British Columbia (the source of 10.7 cm solar flux data) on June 28, and copied us: “Hello Ken, Do you expect today's spike in solar flux will be calibrated downward or will it stand?”

What Elwood refers to is when there is an unusually high solar flux reading, the NOAA Space Weather Forecast Center will report it as a lower value. I always assumed this was because the 10.7 cm receivers in Penticton were overloaded, but as Ken says, whether to change the value or not depends on what the data will be used for.

Ken responded: “I know that in the distant past there were attempts to 'de-burst' flux values. However, it is not possible to do this with any accuracy at all. For example, at first sight it should be easy just to draw a line under the spike and use that value. However, in almost all cases the baseline is elevated by heating and some accelerated electrons beforehand and by heating and residual accelerated electrons afterwards. In some cases the baseline elevation lasts hours. In addition, with the on and off-source telescope motions that are an essential part of every measurement, it is even harder to separate what is going on.

“Those who are using the fluxes for antenna calibration should have exactly what is measured. Some proxy applications need the whole flux too. So in the end the 'correction' process is application dependent, so our policy has been for some decades, tell the user what value we got, with no messing.”

The reading Elwood referenced is the local noon reading in Penticton on June 22, 2015. The three readings that day, at 1700 UTC, 2000 UTC and 2300 UTC were 130.1, 246.9 and 127.2.

Checking we see that NOAA reduced that to 135.

The Australian Space Forecast Centre issued this warning at 0210 UTC June 26:

The CME from region 2371 M7.9 flare is expected to arrive mid
to late in the UT day on 27Jun.

FROM 27-29 JUNE 2015

27 Jun: Minor Storm
28 Jun: Active to Minor Storm
29 Jun: Unsettled with Active periods

ARRL Field Day is this weekend. I hope conditions remain calm!

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

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 download. I’ve had better luck with Firefox than IE.

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 18 through 24 were 82, 74, 89, 79, 77, 61, and 39, with a mean of 71.6. 10.7 cm flux was 150.8, 137.3, 135.4, 131.7, 135, 116.1, and 109.5, with a mean of 130.8. Estimated planetary A indices were 7, 5, 3, 8, 55, 76, and 17, with a mean of 24.4. Estimated mid-latitude A indices were 6, 4, 2, 7, 57, 47, and 15, with a mean of 19.7.



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