The Butterfly Effect, Writ Large
Have you ever heard of the Butterfly Effect? This is part of chaos theory that says a butterfly flapping its wings in Brazil could set off a tornado in Texas. It means that a tiny change in one part of a system can be magnified and ultimately cause something huge elsewhere. It isn’t limited to systems here on Earth — in fact, scientists are finding out that changes on the Sun can have major effects on Earth’s magnetosphere and upper atmosphere. This is a very important area of study — and one that I touched on in a project we (Loch Ness Productions) did for MIT’s Haystack Observatory about spaceweather. You can watch the final episode below, where we talk about how all of Earth’s atmospheric layers are coupled together and how a change in one (say from a bout of space weather affecting the ionosphere) can ripple through the system.
As it turns out, large changes in the Sun’s energy output may have a major effect on the thermosphere — one of the upper layers of our planet’s atmosphere. It ranges up from 90 to 500 kilometers above Earth’s surface, and it’s the place where solar radiation makes its first contact with our planet.
Atmospheric physicists at the National Center for Atmospheric Research (NCAR)’s High Altitude Observatory and the University of Colorado have found that the solar cycle (keyed to the Sun’s magnetic cycle, which produces varying numbers of sunspots over an 11-year period) has other variations, and these affect the thermosphere. If it isn’t bombarded as much by solar radiation, it cools and shirnks.
As it turns out, the Sun’s energy output declined to unusually low levels from 2007 to 2009, a particularly prolonged solar minimum during which there were virtually no sunspots or solar storms. During that same period of low solar activity, Earth’s thermosphere shrank more than at any time in the 43-year era of space exploration. The current research suggests that the Sun was going through a period of relatively low activity, similar to periods in the early 19th and 20th centuries. This could mean that solar output may remain at a low level for the near future. And, the thermosphere could remain smaller than usual. This is good news for orbiting satellites and the International Space Station — they can maintain their current orbits without encountering as much atmospheric drag. On the other hand, during the current solar “maximum”, when solar activity is expected to be at its highest during the 11-year cycle, the Sun’s outbursts like the ones in the SDO animation above could ramp up unexpectedly, threatening us and our technology.
Learning about how the Sun and Earth interact is an important part of astronomy research. Up until a century or so ago, our knowledge of the Sun was pretty rudimentary. Today, after decades of research using both ground-based and space-based observatories (including radar dishes, GPS signals and other methods), astronomers are getting a better handle on the coupled Sun-Earth system.
To learn more about long-term variations in the Sun’s activity, check out these pages at the NCAR/HAO Web site: http://www.hao.ucar.edu/research/lsv/lsv.php.