The K7RA Solar Update
Sweet memories of that 11-day run of sunspots ending on the second day of this month will eventually fade. So far, the number of spotless days is seven -- or perhaps eight by later today -- with the last sunspot seen on October 1. A peek at the latest STEREO images shows two active areas in our Sun's southern hemisphere beyond our direct view, but it is hard to tell if these will emerge as sunspots when they appear over the eastern limb. A rough guess has the first one possibly emerging around October 10, with the second around a week later. Currently, the solar flux forecast shows flux values lower then 70 through October 15, then around 72 during the two-week period from October 16-30. The second spot is seen on the look-ahead image, and is passing into the invisible area, now slightly more than 60 degrees wide in latitude, or about one-sixth of the solar surface.
Sunspot numbers for October 1 through 7 were 11, 0, 0, 0, 0, 0 and 0 with a mean of 1.6. The 10.7 cm flux was 72, 71.6, 71.6, 71.1, 69.9, 68.9, and 68.5 with a mean of 70.5. The estimated planetary A indices were 2, 2, 1, 4, 2, 1 and 2 with a mean of 2. The estimated mid-latitude A indices were 2, 0, 1, 4, 2, 1 and 1 with a mean of 1.6. The average sunspot numbers for the week dropped 15.3 points below the September 24-30 period, and the average daily solar flux for the week declined 2.2 points to 70.5. The same NOAA/USAF forecast predicts the same very quiet geomagnetic conditions we've seen for some time, with planetary A index around 5. Two very small increases are predicted for October 11-12, with an A index of 7, and October 24-25, with the A index at 8.
Regarding the invisible area on the other side of the Sun, this is becoming smaller as the Ahead and Behind STEREO platforms slowly converge. You can figure out the size of the dark area in terms of degrees by going to the "Where is STEREO Today?". The last figure at the bottom of the page is "Separation Angle A with B." Subtract this value from 180 to get the size of the dark area. Currently, early Friday morning, it shows 119.702, which corresponds with a dark area (beyond the sight of the A and B platforms) of 60.298 degrees.
If you go here, you can see how wide that invisible area will be at any date and time in the future. On October 1 at 1800 UTC, the blank area was 61.7 degrees wide. On November 1 it will be 56.3 degrees, and December 1, 51.6 degrees. The non-visible area will be exactly 60 degrees wide around 0021-0028 UTC on October 11. In 2010, that invisible area will shrink from 47.7 degrees on January 1 to 9.3 degrees on December 1. The entire Sun will be visible beginning on February 6, 2011 around 1302-2047 UTC. After that, the blank spot in STEREO's vision will be Earth-facing, and as it grows the information can be filled in from observation here on Earth.
Larry Banks, W1DYJ, of Woburn, Massachusetts, sent in an article from New Scientist magazine titled "Phantom Storms: How Our Weather Leaks into Space." It has many interesting details about our ionosphere and stratospheric warming.
Giles Berry, KE3CR, of New Castle, Delaware, commented about last week's reports of VHF propagation along fog banks. He recalls that in the early 1950s when television first came to the state of Maine, TV reception seemed to improve with fog. Giles notes that on a foggy night he could receive television broadcasts from Boston reasonably well. He was on the mid coast of Maine.
Patrick Hamel, W5THT, of Long Beach, Mississippi, notes that "Here on the Gulf of Mexico Coast, we have always known that when we get fog, we can talk from Florida to Texas 'under the inversion' on 2 meters. It also works on 6 meters, and I regularly heard other stations making contact on 2 meters and then jumping to the higher bands during fog conditions."
Gus Malmberg, SM0EGK, says "When I read WA2AMW's comments about the extraordinary conditions on 2 meters, I recalled what happened early in 1963 when one could listen to all of Northern Europe and see many band I TV stations for a few days. As a youngster, I didn't understand the mechanism, but have since realized that it must have been an extreme temperature inversion. In 1963, we had a solar minimum. I worked for 15 years as a radio and television transmitter engineer for the Swedish Telecommunication Administration, but I have never again experienced something like that!"
Alan Vigeant, KI6HPO, of San Marcos, California, wrote: "I'd like to inform you of past and most recent conditions here in Northeast San Diego County. Since early April, I've been having daily chats with my good friends at the Santa Barbara Amateur Radio Club, situated about 165 miles northwest of my home. I am at 2200 feet of altitude, on the southwest rim of what I like to call the Palomar Ridge, which is about 5600 feet above sea level. Between the two rims is what I call the 'Palomar Trench.' My home is about 12 miles southwest of the Palomar Observatory. Using William Hepburn's Worldwide Tropospheric Ducting Forecasts Web site -- which has proven most helpful to me -- I can pretty much set my watch as to when the duct will be forming. My home is about 40 miles east of Oceanside, California. My signal follows the ducting that occurs in the trench and then goes up the coast of Southern California to Santa Cruz Island, where their 220 MHz repeater is. The past week proved to be a most curious one for me. While I was speaking to the 7 AM SBARC Morning Net, I noticed that the S-meter on my 220 rig (I utilize the club's 223.920 repeater) began to fluctuate rapidly. Looking out my garage side door, I could watch the cloud cover come in from the Pacific; as I looked on, I could actually see that as the cloud cover rose, the meter would decline to an S-3. As the Sun grew higher in the sky and the cloud bank began to recede into the Pacific, the meter would register an S-9 to almost 40 over. At times, during the summer evenings, I could look out along the Palomar Trench and look to the horizon to see if prop was going to be good or not so good for the evening."
Thanks, Alan! Very interesting report.
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.