Fluid Modeling Another way to look at a plasma (or any gas), is as a “fluid”. When you listen to a weather report, they don’t report on the state of the individual atoms in the atmosphere. Instead they tell you the temperature, pressure, and wind speed, in different locations. These represent averages over vast numbers of atoms in the atmosphere: temperature tells you something about the random, “jitter” motion of the particles, pressure tells you about both the motion and number of particles, wind speed tells you the average speed of the particles. You can do the same thing with a plasma. If you divide up the area you’re studying into a grid of boxes, then you can use a different set of equations to track the pressure, temperature, velocity, field strengths, etc., in each box. The equations will tell you how to update the values in each box based on the values in the boxes around them. This approach (a common version is called “MHD”, short for MagnetoHydroDynamics) lets you cover much larger areas of space than a particle model would. But there’s always a trade-off: fluid models can’t tell you what’s going on with individual particles, and sometimes that’s important. And while you save time by not having to track lots of particles, you now have to worry about the size of your boxes. Subdividing your space into smaller boxes gives you more accuracy and detailed information, but increases the number of calculations you have to do. Real Research This might sound a little daunting, but people are doing these kinds of simulations every day. Very fast computers are used, and some computers actually are “massively parallel arrays”, where thousands – or tens of thousands – of computer processors are linked together so that they can all work on the problem in parallel, meaning ‘at the same time’. Here are some links to some research web sites.