With the sun climbing northward to end a seemingly cruel East Coast winter, my attention is turned to it, our closest star. A recent report described the discovery of “seasonal” changes in the sun, highs and lows of about a year during the 11-year sunspot cycle. Currently we are just after a peak in the long cycle.
It wasn’t a particularly high peak, but we did have some solar storms that sent particles to Earth, which excited the aurorae – the “northern lights.” The most recent one, last month, occurred when we had regionally cloudy weather, but one of our cameras that looks each night for the Brown Mountain Lights caught the aurora’s shimmering curtains of light through thin clouds, even though it was a couple of days past the peak. I have seen previous aurorae here that actually went south of the zenith, into our Southern sky.
We are making slow progress coming to understand the sun. It’s a tough study, with complex physics involving magnetic fields that are difficult to simulate with computer models. We need to understand the sun better, though, to know what to expect. Solar flares reaching Earth and inducing electromagnetic waves have brought down the power grid in Canada (power wires are antennae, too!). The greatest outburst ever recorded, in 1859, shut down telegraph lines.
The most peculiar example of the sun’s activity was the Maunder Minimum, a disappearance of sunspots from about 1650 to 1700. Several observers in those early days monitored the sun and reported the absence of spots. Sunspots are areas where the surface gases are a couple thousand degrees cooler, and thus appear darker. It’s counterintuitive that when the sun is heavily covered with these cool areas, it is putting out more energy. That is because the spots are caused by convection currents that move energy out of the sun very efficiently.
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So, the Maunder Minimum, with its dearth of spots, could have contributed to what was already a cold period in our history. What is disturbing is that we do not know why the Minimum happened, but it could happen again. Interestingly, if the telescope had been invented a hundred years later than it was (1608), we would not even know that the Minimum had happened.
Smaller variations of sunspot activity have little effect on our climate. However, it has been found that changes in the sun’s ultraviolet output do have some small effect by way of changing the chemistry of our upper atmosphere.
But, to put it in perspective, all of the small changes are dwarfed by man-made climate change. So, these “natural cycles” in the sun are no excuse for inaction. We can’t count on another Ice Age to save us.
Daniel B. Caton is a physics and astronomy professor and director of observatories at Appalachian State University. Email: firstname.lastname@example.org. More on this month’s column: www.upintheair.info.