The K7RA Solar Update
There are new sunspot groups coming over our Sun’s eastern horizon, but this week has been a quiet one, both in terms of sunspot and geomagnetic activity. The average daily sunspot numbers declined by 50 percent -- from 104.7 to 52.1 -- while the average daily solar flux was down nearly 45 points to 97.2. This is comparing two reporting periods, July 19-25 against July 12-18. Sunspot numbers for July 19-25 were 39, 55, 50, 29, 60, 66 and 66, with a mean of 52.1. The 10.7 cm flux was 100, 92.3, 89.9, 93.7, 96.7, 102.4 and 105.4, with a mean of 97.2. The estimated planetary A indices were 6, 11, 11, 8, 9, 10 and 6, with a mean of 8.7. The estimated mid-latitude A indices were 6, 10, 8, 9, 8, 10 and 6, with a mean of 8.1.
The latest solar flux forecast from NOAA/USAF has flux values at 115 for July 27-28, then 120, 125 and 130 on July 29-31, 135 on August 1-3, 130 on August 4-6, 125 on August 7-8, and 115 on August 9-11, and then bottoming out around 90 on August 17. The predicted planetary A index is 5, 15, 18, 12 and 10 on July 27-31, 5 on August 1-3, 10 on August 4, and 5 on August 5-18. There is possible geomagnetic activity raising A index values to 15 and 12 on August 19-20, and then 18 on August 24-25.
F.K. Janda, OK1HH, sends us his own geomagnetic forecast, and this week he predicts active-to-disturbed conditions July 27-29, mostly quiet on July 30, quiet on July 31, active-to-disturbed again on August 1-2, mostly quiet August 3-4, active-to-disturbed August 5, quiet-to-unsettled August 6-7, mostly quiet August 8, quiet August 9, active-to-disturbed August 10-11, quiet-to-active August 12-13, mostly quiet August 14-15, and quiet-to-active August 16-17.
Astronomy has an article about a July 11 experiment in which a telescope was lifted by a sounding rocket to take high definition photos of the Sun’s corona at extreme ultra-violet wavelengths. David Moore sent a link to a similar article from Astronomy Now website.
Rob Steenburgh, KA8JBY, sent some interesting statistics regarding the NOAA 45 day outlook/prediction for solar flux that is updated daily. You can see the data collection here. Note that the link at the bottom of the page for “Forecast Skill vs Lead Time.” As I understand it, “Persistence” refers to the chance that the solar flux will be the same tomorrow (or up to seven days in the future) as it is today. “Climatology” refers to some value representing a recent average and “Recurrence” is the chance that the solar flux will be the same 27-28 days from now as it is today. This represents one rotation of the Sun relative to Earth. To make this forecast, forecasters look at a combination of these factors, and also whether the activity from four weeks before is increasing or decreasing. What might be interesting is to find out what effect the STEREO mission has on forecast accuracy, because STEREO brought to us the ability to see what is happening everywhere on the Sun. See the continuously updated STEREO image here.
As Rob put it in a recent e-mail: “You are right about the 45 day forecast -- a bit of persistence at the beginning, and then more and more recurrence and climatology later in the forecast. STEREO has helped - we can watch regions coming around on STEREO-B, and in a qualitative sense, tell if they’re larger or smaller. It would be interesting to take a look at the F10.7 stats and see if there’s a statistically significant difference in our forecasts since STEREO went up.”
Rich Zwirko, K1HTV, of Amissville, Virginia wrote: “The 6 meter band opened on Tuesday, July 24 at around 1200 to Puerto Rico, Portugal, France and Great Britain. Two stations on St Pierre and Miquelon also showed up to liven up the magic band. Then around 1515, 144 MHz came alive with E-skip. The first round started around 1525. The last station I heard was W4AS at 1610, then 2 meters quieted down. I didn’t get back on the air until 2110 and found 6 meters hot as a pistol. I worked 66 stations in the next 50 minutes. At 2200, I noticed on the MUF map page that the MUF had climbed to more than 145 MHz to the west of here. I quickly changed frequency to 144.200MHz and started to hear and work E-skip stations to the west and eventually southwest. In this opening, the ionized E clouds favored Oklahoma (11), Missouri (7), Kansas (4), Illinois (3), Florida (3), Wisconsin (2) and one station each from Texas, Arkansas, Minnesota and Iowa. It was a fun day. Too bad it didn't occur during over the weekend during the CQWW VHF contest. My son Andy, K1RA, while driving home from work and operating 2 meter mobile, also got into the fun. He worked N0ICZ, K0NYW, W0BLD and K5SW with 50 W and a mobile whip.”
Reynolds Davis, K0GND, of Lincoln, Nebraska forwarded a July 24 note from Dave Theophlius, W0NRW, of Fremont, Nebraska: “Just like in 2009 and 2010, there was a major sporadic E opening on 2 meters late this afternoon. I had been keeping an eye on the DX Sherlock site all day because the MUF kept popping above 100 MHz in the southeast US. Finally, at 2340 it opened for me. The cloud appeared to be over the Ohio River Valley and I appeared to be on the west edge of people able to make contacts. I did hear W0KT in Omaha also making contacts. CT1HZE, who asked that logs be e-mailed to him, estimated that the MUF rose to 274 MHz as contacts were also being made on 220. The VHF propagation map based on APRS stations was just a big blob of red. The opening only lasted about 10 minutes for me where signals were strong enough to work anybody. At 2340, I worked NT4RT in EM94 in South Carolina, and at 2346, I worked W4TMW in EM84 in Georgia. And just as fast as it opened, it was over for me, although stations farther east continued to make contacts. CT1HZE added a comment on the ON4KST chatroom that in Europe a major opening like today is often followed by another one the following day. So, it might pay to keep an eye open on Wednesday if you are into VHF DX. And my antenna? A 2 meter FM vertical polarized ground plane at 54 feet on my new tower. The VHF/UHF beams are not up yet. So it appears that although VHF SSB/CW operators use horizontal polarization, the polarization during E-skip openings may not be all that important. I think Lance, WN0L, had the same experience during one of the earlier openings. But when Plan A is not operational, it is time to go to Plan B, which is to use anything that is available.”
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 and 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.