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The K7RA Solar Update


Solar activity was very, very quiet over the past week. For the reporting period September 5-11, the average daily sunspot number was only 37.7. Average daily sunspot numbers as reported in this bulletin have not been nearly this low since June 6-12 of this year, when it was 39.6. The last time it was lower was June 21-27 of last year, when it was 26.3.

Australia’s IPS Radio and Space Services issued a geomagnetic disturbance warning at 2330 UTC on September 11. They expect increased geomagnetic activity due to a high speed solar wind stream spewing forth from a coronal hole. Coronal holes are magnetic gaps in our Sun’s corona which allow some of the Sun’s tremendous energy to blast out into space. Occasionally some of it reaches our planet, depending on which way the hole points.

IPS expects unsettled to active conditions on September 12, with a chance of isolated minor storm levels, unsettled to active conditions again on September 13, and quiet to unsettled conditions on September 14.

Predicted planetary A index from NOAA/USAF is 15 and 8 on September 13-14, 5 on September 15-16, 15 and 10 on September 17-18, 15 and 8 on September 19-20, 5 on September 21-25, 10 and 15 on September 26-27, 10 on September 28-29, and 5 on September 30 through October 5.

Predicted solar flux is 95 on September 13, 100 on September 14-17, 105 on September 18-20, 120 on September 21-22, 115 on September 23-30, then 110, 105 and 100 on October 1-3. It then goes to a minimum of 95 on October 4-5, and rises to a maximum of 120 on October 18-19.

F.K. Janda, OK1HH, of the Czech Propagation Interest Group predicts geomagnetic conditions will be quiet today on September 13, mostly quiet September 14, quiet again on September 15-16, quiet to active September 17, active to disturbed September 18, quiet to unsettled September 19-21, mostly quiet again on September 22, quiet to active September 23, quiet again on September 24-25, mostly quiet September 26, active to disturbed September 27, quiet to active September 28, mostly quiet September 29, quiet again on September 30, quiet to active October 1, and quiet again on October 2.

A fascinating article appears this weekend concerning reconciliation of various sunspot records, on the web site, which might seem a little odd, but of course we welcome good verifiable information wherever we can find it. Read it at, but note that you may have to click on the URL twice. First time for me, I saw it redirect to another page on the site, but a second click goes to the article by Brian Owens. The website also appears to be quite slow at times.

Another interesting article, this time (yet again) concerning our Sun’s shifting polarity:

Jeff Hartley, N8II, wrote on September 11 from West Virginia (FM19cj): “Back on August 30 there was some Es excitement with unusual openings into Bear Island, JW9JKA (Svalbard, see on 12 meter phone at 1823 UTC, then around 2100 UTC S5 (Slovenia) and F (France) were worked on 12 meter phone as well as EI6JK (59) and DL5RBW (2212 UTC) on 10 meter phone with good signals as well as DL5AXX on scatter over the South Atlantic and IZ3NYG direct path on 10 CW. Also logged on 10 meters was EA8YB S9+ on SSB.

“Fifteen meters in the past 10 days has been open well to EU between about 1300-2000 UTC, sometimes much later and to Asia well after sunset on good days as well as to Indonesia in our mornings along with SE Asia.

“Twelve meters has been in and out to EU with 10 meters mostly only open to SA and the south Pacific in the evening and late afternoon. On Sept 5, 12 meters opened well to all of EU except Russia logging YL, 4Z, 9A, S5, EG9 (Ceuta),and DL between 1528-1834 UTC. XW8XZ was worked on 15 phone earlier at 1336 UTC with an S5 signal.

“HS0 and XW0YJY were loud on 15 phone around 0050 UTC on the September 8.

“On the September 10, I had a nice run of stations on 12 CW from 1427-1452 UTC including many fairly weak Russians south of Moscow in the third call area.

“FO/KH0PR has been worked several times on 10 CW making a rare IOTA tour including today, September 11 at 1846 UTC.

“Twelve meters seems to open well to EU some days and poorly on other days when the SFI is around 100 and K index is low. It is very difficult to predict. If the flux jumps up to around 120, 10 meters should come to life.”

Note we are only nine days away from the autumnal equinox, on September 22, 2013, at 2044 UTC. As we move from summer toward fall, HF propagation generally improves. For example, if we run a projection using W6ELprop for two months earlier on August 22 using a smoothed sunspot number of 100 from Central California to Japan, 10 meters looks marginal from 2130-0130 UTC. But with the same sunspot number on September 22, conditions look excellent at 2100-0100 UTC and very good from 0100-0300 UTC.

Similarly, on the same dates, from Atlanta, Georgia to Spain on 12 meters on August 22, conditions on 12 meters look fairly good at 1430-2300 UTC. But two months later, signals should be excellent from 1230-2200 UTC on 12 meters over the same path.

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 September 5 through 11 were 75, 41, 35, 24, 13, 23, and 53, with a mean of 37.7. 10.7 cm flux was 110.1, 101.3, 98.5, 95.7, 94.3, 94.9, and 92.8, with a mean of 98.2. Estimated planetary A indices were 4, 5, 4, 6, 4, 7, and 6, with a mean of 5.1. Estimated mid-latitude A indices were 3, 5, 4, 6, 4, 6, and 6, with a mean of 4.9.





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