Solar Minimum
Written by Fraser Cain
The Sun looks calm and steady, but if you take a good look with a telescope you'll see dark spots across the surface of the Sun. These are sunspots, regions of lower temperature than the surrounding surface. The number of sunspots rise and fall over the course of an 11-year solar cycle. When the lowest number of sunspots are on the surface of the Sun, astronomers refer to this as the solar minimum.
Why do the number of sunspots rise and fall? Astronomers aren't really sure, but it's all related to the Sun's magnetic field. Over the course of a 22-year cycle, the Sun's magnetic polarity reverse, and then returns back to its original configuration. After 11 years, the polarity of the Sun reverses; the North Pole becomes the South Pole and vice versa. And then they switch again, returning to the original configuration.
During the solar minimum, there can be times when there are no sunspots on the surface of the Sun at all. When there are many sunspots, there are solar flares and coronal mass ejections. And so, during the solar minimum, there are very few of these events as well. We see much less aurora activity during that period.
The solar minimum would be the ideal time to travel in space because there's the lowest risk of dangerous solar storms.
The last solar minimum occurred in 2004, and the next one will probably occur around 2017.
We have written many article on Universe Today about the solar minimum. Here's one about how the solar minimum doesn't always mean a calm sun.
Here's an article from NASA about a time when there were no sunspots on the Sun. And another about the arrival of the solar minimum.
We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.
Filed under: Astronomy
