The Solar Cycle / by Nathalie Ouellette

 A solar cycle: a montage of ten years' worth of  Yohkoh  SXT images, demonstrating the variation in solar activity during a sunspot cycle, from after August 30, 1991, to September 6, 2001. Credit: the Yohkoh mission of  ISAS  (Japan) and  NASA  (US).

A solar cycle: a montage of ten years' worth of Yohkoh SXT images, demonstrating the variation in solar activity during a sunspot cycle, from after August 30, 1991, to September 6, 2001. Credit: the Yohkoh mission of ISAS (Japan) and NASA (US).

The evolution of our Sun will happen over the course of billions of years. While this timeline is not accessible for us to observe in our lifetime, the Sun’s cycle is! Although less impressive than the changes it will go through over its lifetime, the Sun will see some significant changes over a cyclical period of 11 years.

We have been observing sunspots on the solar surface for millennia, but it wasn’t until the 19th century that scientists started noticing a certain regularity in their appearance and abundance. These sunspots are regions of the Sun’s surface where intense magnetic activity reduces temperature. Although still very hot (2750 to 4250°C), they appear darker in contrast to the surrounding regions that are about 5500°C. They crop up in greater number during a solar maximum, and are often accompanied by solar flares or prominences — ejections of huge clouds of particles and energy from the surface of the Sun.

While the Sun appears considerably more active in ultraviolet light during a maximum, the total energy output only increases by about 0.1%. These maxima are thus not expected to impact global climates, although they can slightly affect some regional weather patterns. The last maximum occurred in 2000, and with a cycle of about 11 years (but which can vary from 9 to 14 years), that would put the next maximum right about the end of 2012: truly great fodder for all 2012-end-of-the-world believers. Happily, you can rest assured that the next solar maximum is of no threat to us, and we have gone through a great number of solar cycles without much of a hitch. While it is true that solar flares and more violent solar activity can sometimes disrupt some of our radio communication systems, we are greatly protected from any actual danger by our Earth’s magnetic field. On the upside, we also see a greater abundance of the beautiful aurora borealis in the polar skies! Furthermore, NASA scientists believe that the upcoming solar maximum may be the weakest one since 1928. Once again, Earth seems to have averted total destruction!