ARRL

News

The K7RA Solar Update

08/01/2008

July ended with no sunspots at all -- save for three days, July 18-20, when one weak sunspot group appeared and faded from view. Sunspot numbers for those days were 11, 12 and 11. Sunspot numbers for July 24-30 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 65.4, 65.8, 66.1, 66.3, 66.3, 66 and 66.5 with a mean of 66.1. Estimated planetary A indices were 11, 3, 5, 7, 7, 3 and 5 with a mean of 5.9. Estimated mid-latitude A indices were 7, 2, 4, 4, 6, 2 and 4 with a mean of 4.1.

This brings us to our practice of presenting the average daily sunspot number for the past three months, then comparing it with a monthly 3 month moving average for the past couple of years. There were 92 days in May, June and July; out of those 92 days, 70 days had no sunspots. This brings us back toward the low of 3 from last fall, centered on October. The average daily sunspot number for the last three months, centered on June, was just 3.7.

Jun 06 28.9
Jul 06 23.3
Aug 06 23.5
Sep 06 21.2
Oct 06 24.1
Nov 06 23.1
Dec 06 27.3
Jan 07 22.7
Feb 07 18.5
Mar 07 11.2
Apr 07 12.2
May 07 15.8
Jun 07 18.7
Jul 07 15.4
Aug 07 10.2
Sep 07 5.4
Oct 07 3
Nov 07 6.9
Dec 07 8.1
Jan 08 8.5
Feb 08 8.4
Mar 08 8.4
Apr 08 8.9
May 08 5
Jun 08 3.7

The outlook from the US Air Force Space Weather operations for many weeks now has shown a predicted solar flux of 66; their prediction from July 31 shows the same for the next 45 days. This tells me that there isn't any period where we might expect more sunspot activity, or at least no way to foresee it. They predict the next geomagnetic activity of any note for August 10, with a planetary A index of 20. They predict a planetary A index of 8 for August 1, then 5 for August 2-6 then 8 again on August 7. Geophysical Institute Prague echoes that prediction with quiet to unsettled conditions for August 1 and 7, and quiet conditions August 2-6.

In response to WD4ELG's comments in last week's Solar Update, Jim Henderson, KF7E, of Queen Creek, Arizona, has some interesting observations: "During these spotless and near-minimum flux conditions, I have seen the extreme divergence of the day-to-day propagation paths as a function of the traditional flux numbers. Allowing for seasonal trends, the differences in direction and quality of openings on a given band from day-to-day where the flux and A and K indices remain nearly unchanged for days, the openings generally show much more relationship to the intensity of the solar wind. From here, the patterns of propagation, under the weak stimulation of near minimum flux, show much more pronounced linking to the dynamic wind speed and composition than to simple 2800 MHz flux measurements. I believe without the positive contribution of the 'ionospheric bias' provided by even a low flux, say 80-85, even a small increase in solar wind has a profound effect on the daily paths."

He continues: "Put another way, the good/bad effects upon propagation from minor solar wind changes (not associated with flares and CMEs) are much more observable when the flux is hovering under 68 or so than when it is higher. At that time, we feel the big effects from the major storms. But it is interesting to note the nuances of propagation (say, by observing the NCDXF HF beacons daily) during a quiescent Sun." Thanks, Jim!

Maurice Picard, W6FQS, of Chico, California, wrote: "I noticed a forecast on a propagation Web site that the geomagnetic field would be unsettled due to a solar boundary crossing. I don't recall seeing reference to this phenomenon in any previous forecasts. What is this boundary crossing?"

Carl Luetzelschwab, K9LA, provided us with this link explaining the term. Carl will be writing the bulletin next week, for Friday, August 8, while your regular author is out of town. Carl will also be on the road, travelling to Rochester, Minnesota for the W0DXCC Convention at the Rochester Amateur Radio Expo. He will post his bulletin from Dubuque, Iowa. Check out Carl's excellent propagation writings.

Another multi-hop sporadic-E report from 6 meters, and this was just last evening. Dave Greer, N4KZ, of Frankfort, Kentucky (EM78ne), reports that beginning at 2322 UTC on July 31, he worked EA8/DL6FAW (Canary Islands) on 6 meter CW with good signals both ways. At 2325 UTC, he worked EA8AK on CW; at 0026 UTC on August 1, he worked EA8/DL6FAW on SSB.

Dave reports that both stations made many US contacts, but also called CQ many times with no takers. He thinks this is a good example of distant 6 meter signals propagating to very specific areas, but not others.= For instance, he saw that EA6SX in the Balearic Islands was spotted on 50.105 MHz over several hours, but Dave never heard him. He also made Canary Island contacts in summer 2006 and 2007, again working stations in pairs, but earlier in the season and earlier in the day. On June 18, 2006 he worked them around 1300 UTC, and on July 15, 2007 around 2200 UTC.

For six years, Dave's station has been on a hilltop (on Skyview Drive!) with a very steep slope toward the East and Northeast. He notes that Northwest Africa is a "real sweet spot" for him on HF, with incredibly strong signals to and from the Canary Islands, Cape Verde, Morocco and Madeira Island. This seems to be true on 6 meters as well. He runs 100 W into a 4 element Yagi at 60 feet. He said his best 6 meter DX ever was in November 2001 when he worked KH2GU in Guam, using an 80 meter horizontal loop antenna at a previous location.

Bill Reichert, N9HH, of Troy, Illinois, reports 6 meter propagation from earlier in the month. On July 9, at 2342 UTC while mobile from EM58br, he worked CT1HZE (Portugal, IM57nh) on 50.084 MHz using a base-loaded quarter-wave whip antenna.

A few days earlier, around 1500 UTC, CU2JT (Azores) called him, but interference from the East Coast prevented him from completing the contact. This was while Bill was mobile in Collinsville, Illinois.

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.



Back