The K7RA Solar Update
Do sunspots matter? Many of us are surprised at how good conditions can be with zero sunspots; the weak solar wind and lack of flares and geomagnetic events likely have something to do with it. Many times during the more active solar periods, sunspots were welcomed, but then some event associated with the higher solar activity would make conditions difficult, disrupt the ionosphere and increase absorption.
For example, look back to the fall of 2003 bulletins via the index. In addition to the text, note the sunspot numbers and A index listings at the end of each bulletin. There were plenty of sunspots, but if you look at bulletin ARLP038 in September, or ARLP044 through ARLP049 around November, there were huge events that drove the planetary A index to 189 during one week and 162 the next. This is hard to imagine today.
Also note the comment in ARLP051 in December 2003 about the relief from geomagnetic disturbances and somewhat higher sunspot activity. Actually, the planetary A index went as high as 43 one day that week, hardly a quiet geomagnetic number, but the previous two weeks were quite a bit calmer than the week prior. Finding those old bulletins was aided by a graph of planetary A index progression from January 2000 to the present on page 10 in the Preliminary Report and Forecast of May 12 here.
Over the near term, it looks like more quiet conditions. We had a nice seven day run of sunspots, but do not know when they will return. Sunspot numbers for May 14-20 were 18, 12, 15, 13, 14, 11 and 0 with a mean of 11.9. The 10.7 cm flux was 73.9, 73.7, 74.2, 74, 72.9, 72.3 and 71.5 with a mean of 73.2. The estimated planetary A indices were 8, 2, 5, 3, 4, 5 and 4 with a mean of 4.4. The estimated mid-latitude A indices were 8, 2, 3, 2, 2, 2 and 4 with a mean of 3.3. Geophysical Institute Prague reports quiet conditions should prevail May 22-28. NOAA and the US Air Force predict solar flux settling back to 70, then rising again June 5-17.
As often is the case, many interesting e-mails arrived in the past few days. Bill Kollenbaum, W4XS/KH7XS, of Laupahoehoe on the Island of Hawaii (the Big Island), has built an impressive station since moving there from Florida. Take a look at the station description and click on the antenna photo here. Bill wrote about working European stations on 15 meters on May 18: "Since moving to KH6 a couple of years ago, any openings to EU on 15 have been far and few between, and I could count on my hands the total number of days I worked any EU on that band. The total number of EU in the log on that band has been around 100, and almost all have been 569 and considerably weaker. On 15 this morning (EU sunset), I put 150 EU in the log from 1930 UTC until 2100 UTC, many of the stations were a true 589 and 599. The opening ran from the Ukraine and Scandinavia, down to LZ and over to EA and G. There seemed to be little geographic advantage to the stations with OH0R calling in with a 589 report, and UK, Italian and Germans all hitting the S9 mark here. Conditions were outstanding. What a difference a small number of sunspots make, coupled with quiet conditions and a big daylight path!"
Bill's path to Europe is a long one. To Spain, the beam heading is not much different from the heading here in Seattle, a polar path at 23 degrees. But the path to Spain at around 8000 miles is much longer than the 5300 miles from Seattle or the 4000 mile path from Ohio or 3400 mile path from Boston.
There were several comments about the comments I made about EMP and vacuum tubes in last week's bulletin. Gene Dathe, NA0G, of Spring Valley, Minnesota, pointed out that vacuum tubes are far more resistant to an EMP blast compared to solid state devices, providing they are turned off. While operating, they could suffer from the same sort of risks.
Bob Voss, N4CD decided to research stories about the great geomagnetic storm of 1859. He sent along this link and wondered if the stories of fires could have been inspired by reports of a "blood red horizon." He sent this link from Spaceweather Canada, and notes there were no fires reported for the 1859 event. Bob notes that the NASA account here actually mentions fires in connection with the 1859 flare. There is also an old 19th century New York Times article here.
I apologize that last week's bulletin reached many people several days late. The bulletin was dated Friday, May 15, but for some reason, it did not get distributed via e-mail until the following Monday night and the date of the bulletin was changed to May 20. The bulletin mentioned that sunspots were just reappearing the day before, but by the time it went out, there were already five days of sunspots. It turns out it had something to do with a string of minor unfortunate events, and HQ staff trying to administer bulletin distribution remotely from ARRL National Convention and the Hamvention held concurrently in Dayton, Ohio. Your author was safe and snug in Seattle (having visited Newington only once, decades ago), and wants to assure everyone that W1AW staff are really a brilliant and clever bunch, but Murphy struck. The report linked from the ARRL Web page appeared as normal last Friday.
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 in The ARRL Letter. 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.