Aurora Prospects from Paul Deans

  
     
  If you think it’s difficult predicting the weather a few days in advance, consider attempting to forecast the appearance of the northern lights as far ahead as September 2008! That’s a tough assignment, and it’s impossible to be completely accurate, but we can make some generalized comments about what we expect to see.  
     
  The 11-year solar cycle has just passed minimum; a new cycle officially began in January of this year. This means the Sun will gradually become more active during the year, but the occurrence of sunspots and flares will remain low, and we’re unlikely to experience a Coronal Mass Ejection — a major outburst from the Sun that often results in a beautiful display of the northern lights.  
     
  What is more likely is that we’ll see auroral activity thanks to coronal holes, which are quite common during periods of low solar activity. These holes are openings in the Sun’s magnetic field that let the powerful solar wind escape into space. When one of these holes is pointed toward Earth, the result can be a lovely show of the northern lights at high-latitude locations such as Iceland. While we can’t predict the appearance of coronal holes far in advance, they occur regularly enough that it’s very likely we’ll see some aurora in September 2008.  
     
  One more thing. For reasons as yet unknown to astronomers, aurora activity peaks just after the spring and autumn equinoxes. This is why we plan to be in the dark skies of the Icelandic countryside a week after the autumn equinox.