The K7RA Solar Update
Sunspots disappeared this week. Five days with no spots is the longest since May 9-19, 2010, when we saw 11 days in a row in which the Sun was spotless. Since then, there has only been the occasional day or two which was spot-free. April 2010 saw 13 consecutive days with no spots, followed by one day in which the sunspot number was 12 (indicating the emergence of a sunspot group with two spots), only to be followed by another spotless day, April 29.
Sunspot numbers for December 16-22 were 23, 11, 0, 0, 0, 0 and 0, with a mean of 4.9. The 10.7 cm flux was 84.1, 81.6, 80.5, 80.9, 77.9, 77.9 and 77.7, with a mean of 80.1. The estimated planetary A indices were 5, 3, 2, 1, 8, 1 and 0, with a mean of 2.9. The estimated mid-latitude A indices were 4, 2, 2, 2, 6, 1 and 1 with a mean of 2.6. With no spots for five days, the average daily sunspot number for December 16-22 dropped nearly 23 points to 4.9, while the average daily solar flux declined 8 points, or a little over 9 percent, to 80.1.
As this bulletin is being written early Thursday, December 23, there may be a spot emerging right in the center of our Sun, when viewed from Earth. It is visible as a white area when viewing the image from the STEREO mission, although this image just shows magnetically active areas in a lighter shade, which does not always correspond to areas with sunspots. Viewing the rest of the image out to the eastern horizon (left side, on solar images) shows no dramatic activity. Unfortunately, the Solar Dynamics Observatory Joint Science Operations Center has experienced a disk controller failure, and until it can be replaced, the latest image they have is from December 19. There is a recent H-Alpha image here.
The noon reading at the Penticton observatory the solar flux rose today to 80.1, precisely the arithmetic average listed below for the prior seven days. Although still pretty weak, solar flux hasn’t been this high since last weekend, Sunday, December 19. NOAA/USAF sees a low solar flux of 78 until December 26-27, when they predict a flux value of 80, then 82 for December 28-29, 84 on December 30 and 90 on December 31 and January 1. They also show low geomagnetic activity with a daily A index of 5, except for December 25, with an index value of 7. They show the A index going back to 5 until the third week in January 2011. Geophysical Institute Prague always has a more detailed outlook on geomagnetic activity, and they show quiet conditions for December 24, quiet to unsettled December 25, quiet December 26, quiet to unsettled December 27 and unsettled December 28-29.
For some, a dead quiet A index on with no sunspots might be ideal for the Winter Solstice, which was on December 21 at 2338 UTC in the Northern Hemisphere. Long nights with low seasonal noise from lightning signal good conditions on 80 and 160 meters, and with quiet geomagnetic conditions, even better.
Chris Scibelli, NU1O, lives in grid square FN32rb in Longmeadow, Massachusetts. On 10 meters he runs 100 W into a 3 element beam at 55 feet. \ He sent us a message after reading about the December 14 E-skip opening on 6 meters in the last bulletin: “On the December 13 after the ARRL 10 Meter Contest had ended, we had about a 4 1/2 hour E-skip opening to Georgia, Tennessee, North Carolina and Virginia. Most of the guys were running ground mounted verticals with 100 W. I went off the air at 0500 as I put in a full 36 hours in the contest and that was enough radio for a weekend. I don’t know if there was any relation to what you wrote about, but what was ironic was we did not have decent E layer openings during the contest. Most of the states I worked at the normal E layer distance were extremely weak -- about an S1. I did have an opening to the West Coast on both the 11th and 12th, but signals weren’t very strong, either. Toward the end of the contest on Sunday, I had a great opening to Argentina and Brazil. Most were 59 to 59 plus.”
Brett DeWitt, W0BLD, lives in Southwest Missouri, near Springfield, and says that he worked a lot of E-skip on 6 meter SSB to both the East and West coasts on December 13. He runs 100 W to a 3 element Yagi at 25 feet, and you can see a log of his contacts by querying the DX Sherlock database here. He wrote: “The opening lasted for several hours. I try to log most of my VHF QSOs on the vhfdx.info site. I worked QSOs from Myrtle Beach, South Carolina to Los Angeles. Some contacts I worked a couple different times over several hours apart. Florida mainly came in first for a couple hours along with South Carolina, Virginia, Georgia, Mississippi and Alabama. Then later in the opening, New Mexico, Arizona and California started booming in here, with Colorado in and out; I think I was able to work one Colorado station. There were also openings several days after the 13th. The band was real good for about a week. I started out in the afternoon and the band was open till I think 9 PM or so, if I recall correctly.”
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 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.