How do sunspots form?

And how do sunspots affect the Earth?

(by Amara Graps)



Sunspots are magnetic in nature. They are the places ("active regions") where the Sun's magnetic field rises up from below the Sun's surface and those magnetic regions poke through. Sunspots are darker than the surrounding areas because they are expending less energy and have a lower temperature. Sunspots often have poles ("polarity") like the south and north poles of magnets.

Sunspots are formed continuously as the Sun's magnetic field actively moves through the Sun. The sunspots have lifetimes of days or perhaps one week or a few weeks.

Here is one scenario that some scientists think explains how sunspots form. Imagine the magnetic field on the Sun as loops like rubber bands that wrap around the Sun, with one end attached to the south pole and the other end attached to the north pole. The Sun is rotating, and different parts of the Sun rotates at different speeds. As the Sun rotates, the magnetic loops wrap tigher and tighter (and get more and more twisted and complicated) until the magnetic field is wound up so tight that the fields ("rubber bands") snap! Where the magnetic field snaps is where active regions (and hence sunspots) on the Sun form.

How do sunspots affect the Earth?

The sunspots don't directly affect us, unless we consider that the Sun's brightness may change by a tiny tiny amount if there are many sunspots. Then the Sun would be less bright, and therefore less sunlight would reach the Earth. But the amount of dimming is so incredibly tiny, that we on Earth wouldn't even notice it.

However, we can look at the related magnetic phenomena on the Sun to sunspots: solar flares, coronal mass ejections, solar prominences. These are solar "storms", a kind of "burp" where the Sun ejects high-speed and energetic particles which are caused by the Sun's twisting and turning magnetic field.

If those energetic particles are ejected in the direction of the Earth, then those particles may affect our power plants here on Earth, or cause pretty auroral displays or those particles may knock out satellites in orbit around the Earth.

If you visit the Space Weather portion of our Solar Resources page, we list many good links to places where you can learn about the Sun-Earth connection. You can also see the Space Weather page.

Here is one place in Sweden that nicely lists the Sun-Earth connections: http://www.lund.irf.se/HeliosHome/spacew2.html

and you can read a detailed, more technical article on the Sun-Earth connection to round out your study.


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Special Thanks to A. Graps