Saturday, March 1, 2008

Why Study the Sun?

When Joe posted about changing his blogging style, it got me thinking about my past blog entries. As I pondered, I realized I really never explained what it is that I actually do. So my next several posts will focus on explaining what solar physics is, why it is important, and what the future may hold for my field of research. Enjoy!


Perhaps the place to start is with the one of the most famous diagrams in astrophysics - the butterfly diagram (this version courtesy of NASA).As you can see, there is a distinct, repeated pattern in the number and latitude of sun spots. Sun spots always come in twos and are caused by strong magnetic fields poking up through the solar surface. These strong, coherent magnetic fields stifle convection in the sun spot, causing in to cool below the temperature of the rest of the solar surface and thus look darker. What the butterfly diagram shows us is that the sun experiences 11 year cycles of magnetic activity.

Why does this matter? For one, these cycles indicate that the highly turbulent convection present in the sun produces ordered, regular phenomena on global scales. This is a classic example of the famous quote by the Nobel laureate condensed matter theorist Phillip Anderson "more is different" (incidentally, Anderson also initially proposed the Higgs mechanism for particle mass). This is something like saying that you can get a pot of boiling water to produce repeated patterns where bubbles start at the edge of the pot, move inward at a predictable rate, and then do it over again. The problem of solar magnetic cycles is a fundamental problem of non-linear dynamics - small, chaotic actions lead to large, organized structures.

The second, more practical reason to care what the sun's magnetic field is doing is summed up quite nicely by the picture below.You may not realize it, but the sun is trying to kill us all. Luckily, we have 92 million miles of separation, the earth's magnetic field, and an atmosphere to protect us, but as people move out of the Earth's protective cradle, there is a increased need to understand why the sun goes through these cycles so that we can better predict when and where these massive blasts of highly ionized plasma will strike.

So why do I study the most studied celestial object in human history? Because despite all of the intelligence that has been thrown at the sun over the ages, we still don't understand fundamentally why it does what it does. We don't understand solar magnetic activity for the same reasons we don't understand things like structure formation in the universe, weather forecasting, or the molecular structure of solids - they are all fundamentally non-linear problems.

And aside from all the deep reasons to study the sun, it is also trying to kill us...


  1. Really good post. The first physics talk I ever went to was at BYU in the summer after I gradated high school. The talk was on sunspots. They where trying to figure out how sunspots effected climate and said there was some evidence that sunspot cycles were partly to blame for mini-ice ages like one in the 1700s.

    1. Do sun spots always form in twos because magnetic filed lines have to enter and exit the sun?

    2. Have you considered trying to write a grant proposal that said "We need money because the sun is trying to kill us?"

    Hey, it might work.

    gain, I enjoyed the post.

  2. In response to Joe's questions...

    1. You're exactly right, sunspots always come in pairs because the field lines have to exit and enter the sun. Incidentally, the polarity of the leading sunspot in a given hemisphere for each 11 year cycle is always the same. Right now in the northern hemisphere of the sun the leading sunspot has the magnetic field pointing into the sun and the trailing spot has field pointing out of the solar surface. Again this is amazing when you consider the fact that these patterns are produced by extremely turbulent convection in an ionized plasma.

    2. While we don't put it in such blunt language, almost all of our grant proposals essentially say "we need money because the sun is trying to kill us" and it's surprisingly effective. Maybe you should try it with your proposals to study, say, the Higgs particle - "We need money because as of yet unobserved particles are the only things standing between us and massless oblivion".

  3. "We need money because as of yet unobserved particles are the only things standing between us and massless oblivion"

    Yes, that would be hilarious, or: "Without cold dark matter galaxies would never form correctly, if we don't study it, and it decays, we would be pretty unprepared now wouldn't we!"

  4. This comment has been removed by a blog administrator.

  5. I have removed the above comment because it linked to an "anti-virus" scam website. Luckily I am not running Windows XP what the above scam was attacking.

    In the future be careful clicking on links from random people.

  6. Are there ever instances in which one sunspot disappears before its partner? Another way of asking this question is, do the magnetic field lines from sunspots ever reconnect or otherwise break? I'm thinking of coronal mass ejections and magnetic reconnection events that occur away from the surface.

    An interesting post, thank you.


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