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Last Post 3/1/2007 4:47 PM by KD Leka

sunspots

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Anonymous

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2/26/2007 10:50 AM
I am interested in learning more about sunspots. What are they composed of and what determines their lifespan? Melissa Larimer

Holly Gilbert

New Member

Posts:81

2/26/2007 12:50 PM
Dear Melissa, Sunspots are regions of very intense magnetic field. The magnetic field is so strong in sunspots that it effectively blocks some of the light coming from the surface (although sunspots appear dark, there is still some light coming from them- it's just so faint compared to the rest of the surface that they appear very dark). Although I'm not an expert on sunspots, I think their lifespans probably partly depend on how complicated the surrounding magnetic field is around and under sunspots. Magnetic fields are constantly being twisted around each other since the Sun doesn't rotate rigidly like the Earth, and when they get twisted enough, a flare and/or solar storm can occur. There are many scientists who currently study how sunspots are generated, how they decay, and how they are related to flares and solar storms. Great question! Holly

KD Leka

Basic Member

Posts:115

3/1/2007 4:47 PM
Hello, all; I'm new to this forum and will likely screw up the formatting. Thanks, Holly, for a good reply regarding sunspots. I'll follow up a bit. The lifetime of individual sunspots (i.e., one dark blotch which is often in a "group" of other sunspots) is fairly strongly determined by just how much magnetic field gets gathered together in it -- in short, big spots live longer than small spots. This is a bit of a trick answer, however, as often smaller spots merge into one another to form bigger spots. Still, that rule-of-thumb is pretty good. The complexity of the fields -- how twisted vs. how simple the magnetic field is -- does play a role in a spot's lifetime, generally if it is very complex then it is shorter lived. You may think of it as burning its stored energy (in the magnetic fields' twistedness) faster rather than just simmering along like a simpler sunspot might do. A very interesting recent example is the sunspot numbered 10944 (on the Sun's east hemisphere now) is returning for I believe its fifth rotation; see http://www.solarmonitor.org/index.php, and then near the top-left, click on previous "rotations" to see its previous appearances). Cheers, -KD