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The K7RA Solar Update


We saw a sunspot on February 11-13, then it was gone. Typical of sunspots recently, it was only seen briefly; this one was a relic of Solar Cycle 23, according to its magnetic signature. For at least a couple of years now, we've been expecting Solar Cycle 23 to bottom out and new Solar Cycle 24 spots to emerge, but the sunspot minimum drags on. Most projections are based on past cycle activity, so according to the timing of past solar minimums, we keep thinking surely soon there will be an explosion of new solar activity, but the Sun seems to tease us. Sunspot numbers for February 12-18 were 11, 11, 0, 0, 0, 0 and 0 with a mean of 3.1. The 10.7 cm flux was 69.7, 70.1, 70.1, 69.6, 69.5, 70.6 and 69.8 with a mean of 69.9. The estimated planetary A indices were 4, 3, 14, 10, 3, 1 and 2 with a mean of 5.3. The estimated mid-latitude A indices were 1, 2, 9, 6, 2, 1 and 1 with a mean of 3.1.

Our recent experiment with a 3-month moving average of sunspot numbers (look here for the latest one) points to August 2008 as the possible solar minimum. If it turns out to be the end of Solar Cycle 23, that would make that cycle nearly 12 years long, only a little longer than the less-than-11-year average cycle length. Tomas Hood, NW7US, of Stevensville, Montana, has a nice image showing the transition from Solar Cycle 23 to Solar Cycle 24 sunspots. I believe the vertical axis represents number of actual sunspots per month, rather than sunspot number, which is entirely different. Tomas's Web site has information on radio propagation; you can also hear his twangy guitar when you go to that page.

Geomagnetic conditions were quiet this week, although February 14-15 saw moderate activity. The middle-latitude Fredericksburg A index was just 9 and 6 on those days, and the Planetary A index was 14 and 10. The high-latitude College A index -- measured near Fairbanks, Alaska -- was 25 and 22, indicating possibly disturbed conditions over polar paths. February 16-19, and possibly into today, show very stable and quiet indicators, similar to the January 7-8, 11-12, 21-25 and February 1-3 and 6-13 periods. All those ones and zeroes for K and A index tell the story here.

Geomagnetic conditions should continue to remain quiet. NOAA and the US Air Force predict a flat solar flux around 70 for the next month. The predicted planetary A index for February 20-23 is 8, 12, 8 and 5, continuing at 5 until March 3 when it may rise to 10. Geophysical Institute Prague predicts quiet conditions for February 20-26, except for unsettled conditions February 21-22.

There were a couple of bugs with some links in last week' Solar Update. The bulletin as displayed on the ARRL Web site showed one of the links, mms:// with the beginning unhighlighted, so when users clicked to try to watch the VR2BG video on OTH radar, they were instead taken to a similar address beginning with http:// that does not work. Instead, highlight the whole URL -- including the mms beginning - and hit "CTRL-C" to copy. Open another browser and paste the URL into the Web address field by clicking in the field and then hitting "CTRL-V" and then the "Enter" key. Or you could just click on the corrected link above.

Similarly, the link, although correct, caused the server to display an anti-hotlinking error message as it detected the redirect from the ARRL Web site. This can be solved like the earlier problem with the mms:// URL. Just highlight the URL, then copy and paste it into another browser. Works every time. Thanks to George Mackus, AB0RX, of Maryland Heights, Missouri, for alerting us to the problem.

Find more information on the Chain Home Radar system -- Jim Muiter, N6TP, of San Mateo, California, recommended this Web site.

Greg Andracke, W2BEE, of Pine Plains, New York, is off to Middle Caicos Island (IOTA-002) from March 2-12 as VP5/W2BEE. Greg will be operating CW with just a doublet antenna, and if not on vacation, perhaps he is there to film another documentary. Greg is a cinematographer; recently I watched his excellent 2007 Academy Award winning documentary, Taxi to the Dark Side, via a DVD from my local library. Not sure which HF bands he will be on, but he said he will be operating casually.

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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