The K7RA Solar Update


The average daily sunspot numbers dropped from 50 (on the reporting week ending January 5) to 38 on January 6-12, and now 21.3 on January 13-19. Sunspot numbers for January 13-19 were 14, 11, 11, 15, 36, 34 and 28, with a mean of 21.3. The 10.7 cm flux was 79.5, 79.3, 80.2, 80.3, 81.8, 81 and 80.8, with a mean of 80.4. The estimated planetary A indices were 6, 7, 5, 3, 4, 3 and 6, with a mean of 4.9. The estimated mid-latitude A indices were 4, 6, 2, 3, 4, 3 and 5, with a mean of 3.9.

The average weekly solar flux over the same three periods dropped from 89.5 to 83.8 to 80.4 over this past week. The latest solar flux prediction shows a value of 82 for January 21-27 and 88 on January 28-30, followed by 87, 85, 85, 84 and 84 on January 31-February 4. Geomagnetic predictions have the planetary A index at 5 over the next couple of weeks, except for a value of 7 on January 22 and February 2-4. Geophysical Institute Prague expects quiet conditions on January 21, quiet to unsettled January 22 and quiet January 23-27.

Carl Luetzelschwab, K9LA, has a propagation column in WorldRadio Online for February 2011 called “Using Antenna Height As an Aid to Propagation.” Of course, the higher the better -- right? But Carl calculates the propagation modes over a particular path at a particular date and time, showing how the antenna radiation pattern at different elevations would affect the signal. He used the propagation prediction program VOACAP, and this program as well as W6ELprop, while and others use the monthly predicted smoothed sunspot number. The latest predicted smoothed numbers for January, February and March 2011 are 39, 43 and 47. They show it increasing four points every month through July, then 3 points from July to August and 2 points per month after that, through June of 2012, followed by 1 point per month increase through October 2012, then one point every 2 months until a peak of 90 in 2013 during February through July.

If you go here and set the time, month and year, it generates a coverage map with your station at the center. Color coding on the map shows the percentage reliability. For location, there are many prefixes selectable in a drop-down menu, or 59 locations in the United States and 16 across Canada. As an alternative, you can enter a four or six character grid square. You can find six character grid squares by call sign online after you create a free account and log in. Then another drop down gives you a wide variety of antenna heights for vertical, dipole, 3, 5 and 8 element Yagi antennas, as well as a theoretical isotropic radiator.

Any of nine HF bands -- 80 through 10 meters -- are selectable in another drop down. The sunspot number used is the International Sunspot Number, which is lower than the NOAA Boulder number reported in this bulletin. For each month, they use the predicted smoothed sunspot number for that month.

This tool is fun to play with! One cool trick is to open the page in two web browsers, set up parameters (for example) to have everything equal except the year, then use alt-tab (if you are using Windows) to take you back and forth between the two maps, easily seeing the differences. Or you could do the same thing with a page open in each of multiple tabs in a single browser. I actually found this easier than doing the alt-tab selection.

So for instance, I set up five tabs in my browser -- one for each month, January through May 2011 -- and used 10 W on 10 meters into a dipole at 10 meters high at 2100 UTC. It is fun to click through each tab and see how my 10 meter coverage would change over the end of this winter and through spring.

Strangely, they have separate pages for the 11 meter band for each type -- point-to-point and area coverage. I suppose there are still operators on the Citizens Band who might want this, and for the extreme (and illegal) CBer, you can actually select up to 1500 W and an 8 element Yagi at 198 feet! Doing this for March, 2013 sets up an impressive coverage map. I can hear the howl of heterodynes now.

Scott Bidstrup, TI3/W7RI, sent in an article about creation of a three dimensional model of the ionosphere that helps explain F layer anomalies in equatorial regions after sunset.

Patrick Dyer, WA5IYX, of San Antonio, Texas (EL09ql), wrote last week: “Several 6 meter ZL/VK-US events occurred since around Christmas, mostly involving just K6QXY or N5JEH (NM). (Check the lookback/search features here, here, here or here using the ZL/VK calls noted.). Iowa and Illinois got into the January 10-11 event. The best guess, as this is near the Es peak in each hemisphere for the winter and summer seasons, is Es-Es-F2F2-Es-Es (add another -Es for the W0/W9 path). F2F2 is the chordal hop over the geomagnetic equator where the high ionization levels and effective tilts permit very low angles of incidence (thus giving much higher MUFs than one would expect from a ‘flat’ layer). As most of the Es hops involved are over water there is generally no evidence/warning of any intermediate signals from along that path. The January 10-11 event, with its concentrated US hotspot footprint in Arizona, shows this very well as W0/W9 had Es linking them to/thru Arizona! Even during the Solar Cycle 21-23 peak years, 6 meter VK/ZL paths that far to the US Northeast were rare versus the numerous events to W6, south W7, W5, and south W4.”

Peter Laws, N5UWY, of Norman, Oklahoma had a response to W1YO’s comment in last week’s bulletin that “I have been through five solar cycles and this one is not normal”. Peter writes: “With all due respect to W1YO, a sample size of five is hardly enough to make a judgment about what is normal. This cycle may be different from the previous four or five, but we have little evidence to determine if any of them is normal. In all, we only have good data on the last 24 or so cycles, and less-accurate data for few more cycles before that. But our nearest star is about 4.5 billion years old. That’s more than 400 million solar cycles!”

True enough, but “normal” expresses what you are accustomed to, as well as what expectations are. I think many of us wish that cycle 19 was normal, as in, not unusual and that Solar Cycle 24 was normal as well.

Speaking of what is normal and what is not, occasionally you can read something in the press, quoting someone who seems to be getting it terribly wrong regarding solar activity. There was a “long range weather forecaster” quoted this week in the Australian press who says he uses sunspot activity to make his predictions. He was quoted as saying that “There is a huge amount of solar activity and solar flares at the moment.” Don’t believe it? Read it here.

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.