With John Tierney away, Williams College astronomer Jay M. Pasachoff was on TierneyLab yesterday, describing his journey to China to study the total solar eclipse that will begin on July 22, the longest eclipse this century. Check out this great picture of a total solar eclipse in Siberia last year:
I just checked not only the weather outside my window (which overlooks dramatically deep valleys and wooded mountains) but also the space weather. “Space weather” is the current name for the relationship between the Sun and the Earth, since the Sun gives off particles in an outflow called the solar wind and bursts of X-rays and other radiation, affecting the Earth. Today’s monitoring at spaceweather.com shows that there are no sunspots on the Sun — again. More detailed monitoring at solarmonitor.com shows that other images of the solar surface, in X-rays, magnetic field, hydrogen light and ultraviolet light, are all smooth rather than showing bright areas that mark the sunspot regions. Sunspots are places on the Sun where the magnetic field is thousands of times stronger than the average magnetic field. But there have been hardly any for about two years now; the Sun has been blank for more than three quarters of the time. This is very unusual, even for a low phase in the approximately 11-year sunspot cycle. And we have been in this low phase for at least 12 and a half years, getting to a worrisome point. Nobody knows why it’s taken so long — or even definitively if sunspots will reappear. [An article on the missing sunspots will appear Tuesday in Science Times.]
Scientists are particularly interested because of work by the recently deceased astronomer Jack Eddy, who found a period in the early 1700’s where there were no sunspots for decades. That period corresponded to a cool period, at least in Europe, known as the Little Ice Age. Nowadays, scientists monitor the “total solar irradiance” (it used to be called the solar constant, but it turned out not to be constant). It is about 1/10 of a percent less at sunspot minimum than at sunspot maximum, which has to be taken into account in models of global warming. The effect is much too small compared with our human contributions to the atmosphere to be important for global warming calculations, but it should be included in the models.