If you want to go to Iceland to see the Northern Lights, you might want to go fairly soon because it looks like the Sun is about to enter a period of low activity.
Our Sun goes through an 11-year cycle between a solar maximum and a solar minimum. When it is most active, it can have several hundred sunspots a year on its surface, dark areas of magnetic activity. During a minimum, however, these drop dramatically, leaving the Sun looking blank.
A decrease in sunspots is an indicator that the Sun is heading towards the minimum. And for 15 days starting on March 7 this year, NASA’s Solar Dynamics Observatory (SDO) observed a spotless Sun.
“This is the longest stretch of spotlessness since the last solar minimum in April 2010, indicating the solar cycle is marching on toward the next minimum, which scientists predict will occur between 2019-2020,” said NASA in a statement.
We don’t entirely understand the solar cycle, but we do know it affects the Sun’s activity. This means, in those years, less particles will hit Earth’s atmosphere – and thus our aurorae will be less impressive, appearing mostly green rather than other colors like red.
We’re currently in Solar Cycle 24 (solar maximum was reached in April 2014), which is the 24th recorded cycle since sunspot activity was first recorded by Swiss astronomer Johann Rudolf Wolf in 1755. It’s actually believed to be the weakest cycle in more than a century, since Solar Cycle 14 in 1906.
Interestingly, while there isn’t much to worry about from a solar minimum, it does increase the amount of cosmic rays hitting Earth. Normally, the solar wind prevents a majority of cosmic rays reaching Earth, especially during a solar maximum.