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No sunspots yet, and the sun has been blank for 17 days. For a week, one sunspot was visible prior to the spotless period, and that followed a 20-day spotless run. NOAA and the US Air Force have predicted daily solar flux (the amount of energy we receive from the Sun at a wavelength of 10.7 cm or 2800 MHz) right at 70 recently, but bumps that to 72 for March 1, continuing into April. This is a minor change, but perhaps this signals that forecasters don't expect any more spots during February.
NOAA also predicts low geomagnetic activity until February 28-29 with the planetary A index at 5 through February 26, then 8, 20, 15 and 12 through March 1. Geophysical Institute Prague predicts quiet conditions February 22-26, quiet to unsettled February 27 and unsettled February 28. Sunspot numbers for February 14-20 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 70.6, 69.7, 70.3, 71.1, 71.2, 71.7 and 70.9 with a mean of 70.8. Estimated planetary A indices were 15, 10, 9, 5, 12, 12 and 7 with a mean of 10. Estimated mid-latitude A indices were 10, 8, 8, 3, 9, 10 and 5 with a mean of 7.6.
The days are getting longer, so openings should be longer on the higher frequencies. For instance, on February 1 the 20 meter path from California to Japan would be open 2200-0100 UTC. On the last day of this month the path should be open longer, 2130-0200 UTC, but signals weaker by about 10 dB. At the vernal equinox on March 20, that opening would stretch from 2100-0400 UTC.
On February 1, 17 meters to Japan would have an opening about 2230-0000 UTC, but at the end of the month it would lengthen to 2200-0100 UTC, and signal levels barely lower. By March 20, that 17 meter opening should stretch from 2130-0300 UTC. All of these times and frequencies assume zero sunspots.
Chuck Miller, N6KW, of Seattle, Washington, noted that on Sunday in the ARRL DX CW Contest he had a good 40 meter opening to Europe from his place in Seattle during daylight, from 2300-0000 UTC; he worked OK5R, TM9R, IR4X, F8CMF and OM5ZW. From Seattle to Europe last Sunday, this wouldn't be unusual, although signals would be strongest 1-3 hours later.
Kevin Seeger, WD0AVV, of Corona, California, wants assurance that this bulletin will identify Solar Cycle 24 sunspots as they appear; he also needs a method to find out for himself what the polarity is. Yes, we will keep readers informed of new spots and identify them as Cycle 23 or 24.
A way to check to see what Solar Cycle a sunspot belongs to is to look at the magnetograms from the SOHO spacecraft. If you see a sunspot with black on the right side and white on the left, this is a Cycle 23 spot. A Cycle 24 spot will lead with white on the right and black on the left. You can see this by searching the archives for images from early February. Under image type, select "MDI Magnetogram," select the "Images" option under Display and enter 2008-02-02 for Start Date, 2008-02-04 for End Date, then click "Search." The result will be a series of images of Solar Cycle 23 spots.
Randy Wing, N0LD, of Rose Hill, Kansas, wrote that he found it interesting that when there were no sunspots, "I was working Ducie Island on 10, 12, 15, 20 and 80 meters." Very impressive, but check out his nice antennas.
George Munsch, W5VPQ, of San Antonio, Texas, had comments about recent 160 and 75 meter discussions. "The 160/75 meter propagation conundrum arises because the F-layer is needed for propagation and the D-layer must be weak or absent to minimize absorption. When both layers are weak or absent during these long stretches of no sunspots, the bands aren't going to be very useful, which has been my observation here in Texas, although domestic long skip on 75 in the mornings has been pretty good. The only problem is that many of the stations heard are in small local cliques who are accustomed to talking among themselves and dont want to be bothered with contacts to out-of-area 'intruders.'"
George Coleman, AA4LR, of Loganville, Georgia, had an interesting observation about this solar activity minimum we are experiencing: "One thing I've noticed that separates this solar minimum from others is the level of the solar flux. Seems like we've had very, very few days of solar flux lower than 70; however, I seem to remember at least from the solar minimum in the 70s and 80s that solar flux got as low as 66 and stayed there for a considerable period of time. I remember listening to WWV over a period of several days and finding that the solar flux levels were unwavering from 66."
I think George is right. Solar flux hovers around 70 or above, but doesn't go down to 66-68 this time. For instance, May 21-30, 1996 the average solar flux was 66.7. The average solar flux for all of September and October 1996 was 69.3. We are cherry-picking the data here, but for the seven days of July 18-24, 1996, the solar flux was 66.8, 64.9, 66.1, 65.4, 65.1, 66 and 66.7 -- an average of 65.9
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.
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