Thursday, July 30, 2009

Of sunspots and Stradivarius

Amateur radio operators watch the latest sunspot reports much like investors watch Wall Street tickers. Are we coming out of the bottom of the lastest cycle? Are there signs of new spots on the solar disk?

As we all know, sunspot activity has a major effect on long distance radio communications. As sunspot activity increases, so too does propagation on shortwave frequencies. Sunspot cycles last about 11 years, and we're currently at the bottom of Cycle 23. But as many have noted, Cycle 24 seems to be slow in starting, leading to concerns that we may be entering another Maunder Minimum.

The Maunder Minimum (aproximately 1645 to 1715) was a period of exceptionally low sunspot activity. Whether a direct correlation exists between sunspots and global temperature is open for debate, we do know that this period corresponded to what became known as the "Little Ice Age" during which record low temperatures were experienced across North America and Europe. We also know that the variation in cosmic radiation bombarding the earth was affected, and this was reflected in the amount of carbon-14 found in tree rings. It's hypothesized that the colder temperatures led to slower tree growth, resulting in a very hard wood that Stradivarius used to such great advantage in crafting his incomparable violins.

Similar periods of extended solar minimums have been observed or indirectly detected via carbon-14 dating from 1450 to 1540, and again from 1790 to 1820. In fact, over the past 8,000 years the sun has spent about a quarter of its time generating few or no sunspots.

Nonetheless, scientists at the National Solar Observatory in Tucson, Arizona say the solar mechanism that generates sunspots is functioning just fine, albeit more slowly than usual. According to these scientists, the solar jet stream has reached the 'critical' latitude, and the number of observable sunspots is already on the rise. If this proves true then we can expect to see marked improvement in propagation from 20 meters all the way up through 6 meters nearly any time of day.

And that's music to my ears.

Steve KB3IHX

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