Wednesday, August 12, 2009

The Research Doldrums

Back when nautical vessels were 100% wind powered, there was a saying that what sailors feared more than storms were calms - times when the wind simply refused to blow, leaving the ship effectively stranded. Near the equator there is a region called the doldrums where strong solar heating of the earth's surface creates strong vertical motions that tend to stifle horizontal winds, leaving ships stuck.

Anyone who has been in basic science research for a while can tell you that research is a little like sailing in a wooden sailboat on the wide oceans. Sometimes you discover the New World, sometimes you get raided by pirates, and sometimes you get stuck in the doldrums, baking under a hot sun, waiting for the winds to pick up and get you moving again. And although modern researchers have more options than becalmed 17th century sailors, sometimes it doesn't seem that way.

I am currently stuck in the doldrums. I am trying to improve our models of the sun by improving the way we model physics at small-scales. This falls under the long-standing problem of how to model turbulence, which has an annoying tendency to take large scale motions, break those motions into increasingly smaller scale motions, and finally dissipate the kinetic energy in small scale motions via viscosity. It's a hard problem and I'm not trying to solve it so much as use what little insight others have gained to improve our models of the sun.

I have two so-called turbulence models that should do this, but when I implement them into our code sadness ensues. One of these models seems to upset the fundamental balances of how energy is transported outwards in the solar convection zone and defies all my attempts to understand why it does so. The other appears to be extremely computationally expensive making it more work than it is worth. I have been working on these two problems for several months now, but every time I make a little progress and I feel a slight breeze and begin to think the wind might be picking up, it dies down again. And so I remain stranded on my little boat of research, praying for some wind.

Ironically, the sun remains in the doldrums as well with almost no magnetic activity. Perhaps it can't get its small-scale turbulence models to work either.


  1. Nick, I think my research can be summarized as: "Thinking he was about to discover the new world he quickly realizes he is in fact being raided by pirates. His only hope is that a post doc or thesis adviser can save him from destruction."

    Good luck with all that computational stuff, I'm sure it can be very frustrating at times. However, the world needs people to work out the messy computational stuff.

    Also, what is the deal with the sun being so quiet these days?

  2. Yes, during these times it's nice to have handy an advisor and - in my case - the former grad student turned researcher at a national lab that wrote the code I use. I think I need to borrow some of their wind...

    And as far as the sun goes, it seems to be just taking a break. It's been 32 days since the last sunspot was seen. The new solar cycle should be well underway at this point so the question of why no sunspots has pretty much everybody scratching their heads. But on some levels, since we are dealing with an extremely chaotic system, it's not really surprising that every now and then it does something unexpected.

  3. How big is the sun compared to the other stars? Do all stars have sunspots? Are they not having sun spots too?

  4. Tammy,

    Stars range from about half the size of our sun to possibly 100 times more massive, however there are far more small stars than large stars. If you take the mean stellar mass our sun is small, but if you take the median stellar mass you get almost exactly the mass of our sun. Basically, our sun is a fairly average star.

    We are still unable to create images of other stars (with a few exceptions) so we can't see star-spots directly, but from indirect evidence it appears that almost all stars create magnetic fields and therefore have some form of star-spots. Our sun is less active than most other stars we have observed, but that is largely explained by the fact that our sun rotates more slowly than most other stars like it. You can think of a stars rotation as the power source for spots - the faster the star spins the more spots it will have.

    Our sun undergoes 11-year cycles of sun-spot activity. Right now it is at least activity phase of the cycle, but this minimum is far less active than normal. In fact, you have to go back to the 1920's to find a minimum that what this quite.

    The data is very limited, but it appears that some other stars also go through cycles, but we don't yet have enough data to tell if that is normal.

  5. I should note however that our computer models of other stars indicate that they should undergo cycles of magnetic activity in much the same way our sun does.


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