The K7RA Solar Update


We are definitely continuing to see robust solar activity. Sunspot numbers for October 6-12 were 99, 88, 61, 71, 87, 113 and 149, with a mean of 95.4. The 10.7 cm flux was 123.9, 122, 118.4, 121, 126.4, 130.1 and 134.1, with a mean of 125.1. The estimated planetary A indices were 7, 7, 7, 13, 3, 4, and 6 with a mean of 6.7. The estimated mid-latitude A indices were 6, 4, 5, 8, 2, 3 and 4 with a mean of 4.6. You can always check here for daily images of the Sun, and lately, it’s been full of spots. You can also use the archive feature to view the position of sunspots for previous days.

The average daily sunspot number for the week (95.4) was about the same as last week (96.7) and the week before (96.1). The number hasn’t stayed steady though, with daily variation as low as 82 and as high as 126 over the past two weeks. You can check here for daily updates showing which numbered groups appeared and faded away, along with the relative area covered by each one.

The latest forecast from USAF/NOAA has the solar flux at 135 on October 14-15, 130 on October 16-20, 125 on October 21-November 2, 120 on November 3-5 and 125 on November 6-8. The predicted planetary A index is 5 on October 14, 8 on October 15-17, 5 on October 18-27, 8 on October 28-30 and 5 on October 31-November 2. Geophysical Institute Prague predicts quiet conditions on October 14, quiet to unsettled October 15, unsettled October 16, quiet to unsettled October 17 and quiet October 18-20.

There has been a lot of 10 meter activity lately, and Jeff Hartley, N8II, of Shepherdstown West Virginia, sent this last week: “Today, October 7th, the solar flux index was only 125 and 10 meters was wide open to Europe at 1220 (65 minutes after sunrise) with a very large amount of activity. As we move into October, a bit lower solar flux index will produce openings equivalent to those around the equinox two weeks ago with higher MUFs. I started off the day breaking a European pile up calling 7Z1TT in Saudi Arabia who was S9. I called one British station running a vertical and 100 W who was S9 and two stations called me when signing. Then I moved up to 28.530 MHz where there was still plenty of activity and ran off about 10 QSOs before having to stop. Ten meters was wide open to Moscow and Great Britain, which has been left out of many recent openings; M0RAD was S9+25 dB and I worked XU7SSB in Cambodia on 15 meters CW S7 around 1300. T32C on East Kiribati has been loud on all bands in the past week and I’ve logged him on every HF band except 40 meters, including both modes on 15, 12, and 10. Ten meters is routinely open to the Rockies and West Coast an hour or more after sunset. I was lucky to find VK4FAXA running 10 W calling in from McClay Island (OC-137) on 10 meters last night. Conditions on 10 meters have been great, except over the pole from here, and I have not seen that many Japan/Asia openings.”

Michael Gutman, K2CHM, of Mashpee, Massachusetts, writes: “Propagation on 10 meters is certainly feeling a lot like 1958. I worked T32C on East Kiribati on October 9 at 7:25 PM on 28.485 MHz and he was 5-9. It is impressive to me, as I run only 100 W to a dipole in the attic here at sea level on Cape Cod.”

Mark Lunday, WD4ELG, of Greensboro, North Carolina, wrote on October 11: “Nothing gets the blood moving like a 10 meter opening at sunrise! China, Azerbaijan, St Helena, India, Sri Lanka and of course tons of European stations, all at 0800 local, and all audible on wire antennas. This feels almost like 2001 all over again! In fact, 10 and 12 meters have been spectacular this week.”

We also received a report on 6 meters. Anibal Dos Ramos, HK3R of Bogota, Columbia, said that on Sunday, October 9, he made his longest distance 6 meter contact yet. It was 2318 UTC when he contacted KH7Y on both SSB and CW, and he heard KH7Y for about 30 minutes with S9 signals. He estimates the distance was 8897 km (5528 miles) and he heard no other Pacific stations. There is much more on six meters and the recent meteor showers. Perhaps we can report on that next week.

Roger Harrison, VK2ZRH, sent an interesting e-mail about propagation of VHF signals from Dubai in the Middle East to the Far East. He wrote: Over September 12-16, United Arab Emirates TV signals from Dubai on 48.25-53.75 MHz were being copied in Shenzhen in Southeastern China, Hong Kong and the Philippines, which are all in the UTC+8 time zone; Dubai is UTC+4. Dan, VR2HF, is the HK contact, while George, DU1GM, is located 80 km south of Manila. The 48.25 MHz video signal typically reached S9+20 dB on peaks. The 53.75 MHz sound channel was received for short periods when the MUF peaked. Optimum reception time was around 1200-1300 UTC, although sometimes signals were received in Hong Kong as early as 1130 UTC (1930 HK local time).

“The propagation path ranges from about 5900-7200 km and is generally in daylight in mid-September. As this is the equinoctial season, when the occurrence of sporadic-E is a minimum, I thought the propagation was most likely to be F2, requiring two hops of about 3000 km each to Shenzhen/Hong Kong, and about 3600 km to DU1. Dubai is located about 18 degrees N geomagnetic latitude, while Shenzhen and Hong Kong are at about 11-12 degrees N geomagnetic latitude. Manila is directly beneath the geomagnetic equator. The propagation path is largely beneath the northern Equatorial Ionospheric Anomaly (aka the Appleton anomaly) in the F2 region, which lies generally between 10 and 20 degrees geomagnetic latitude north (another forms south of the geomagnetic equator). It is the region of high electron density that forms late morning local time, builds during the day and can last 6-7 hours into early evening.

“For the Dubai-to-Shenzhen/Hong Kong path, the first F2 reflection point would be 1500 km east of Dubai, near the northern extent of the EIA, and in the UTC+5 time zone. The second F2 reflection point would be about 4500 km east of Dubai, in the UTC+7 time zone and near the middle of the EIA. To support 48 MHz propagation, foF2 at each F2 reflection would need to be above 14.5 MHz, as a 3000 km F2 skip has an M-factor of about 3.3.

“The only vertical incidence ionosonde with available online data that I could locate in the EIA zone is at Guangzhou, about 100 km northwest of Shenzhen, and 140 km northwest of Hong Kong. Although at the propagation path’s eastern end, the growth of the EIA “follows the Sun” westward and the Guangzhou foF2 values provide a good guide as to how the EIA develops during the day, from which we can infer likely foF2 values west along the propagation path. NOAA’s Space Weather Prediction Center lists the Guangzhou ionosonde’s parameters here.

“For September 13, foF2 was above 16 MHz from 0500-1100 UTC, which implies that the highest electron density of the EIA covered a longitudinal extent of six hours. The 1st F2 reflection point will determine when the path opens as the second reflection point will be well covered by the EIA. As the openings commenced around 1130-1200 UTC, the foF2 at the first reflection point must have reached 14.5 MHz at 0830-0900 UTC, which is 3.5 hours after foF2 hit 16 MHz at Guangzhou. The discrepancy can be put down to the fact the first reflection point is closer to the northern edge of the EIA, where the electron density would take more time to accumulate to the high values found near the middle of the EIA. Undoubtedly, the propagation experienced was supported by 2-hop F2 skip east-west along the EIA.

“The Dubai-DU1GM path is reported to experience longer durations and higher signal strengths than the Dubai-Shenzhen/HK path. Each skip is about 3600 km, just shorter than the maximum F2 skip of about 4000 km. For F2 skips of this length, the M-factor is about 4, so foF2 only needs to reach 12 MHz to support 48 MHz propagation, and the EIA achieves this earlier and sustains it longer. For the record, the 10.7cm flux over September 12-16 was 124, 129, 143, 141 and 143, while the A index was 17, 11, 5, 4 and 2 (NOAA weekly figures).”

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.