Progress on Numerical Simulations Trapped nonneutral plasmas are systems subject to relatively few physical laws, yet exhibiting a startling variety of intriguing behaviors.
In the example presented below, a computer simulation follows the time evolution from a radial distribution with a hollow core to the more stable distribution with density decreasing with radius. The disruption in the first few frames is driven by the "diocotron instability". Clumps are seen to form. Smaller clumps are swallowed up by merger with larger neighbors. Over time the few remaining clumps migrate to the center, displacing the low density halo to the surface. By the end of the 106 frames, the plasma is seen to be approaching cylindrical symmetry again, having filled in the hollow center by turning itself inside out.
This animated gif image is 314 kb in length, and so may take some time to download via modem. It should repeat when viewed by a conforming Browser. The number on each frame is elapsed time in simulation units. Note that the time interval between frames changes from 10 to 20 to 40 units to keep the total presentation to a tolerable length.
Visit Damon's website where you will found more about the computational technique and can view another animated gif of a two-plasma merger, which can be compared to experiment. (You will need to enable Java to start his animations.)
There is also work in progress on a quite different computational method for following the time evolution of a nonneutral plasma. A first glimpse of a fluid-in-cell treatment in 2D of a beam-plasma interaction.
The left button below returns you to the plasma site, while the right button takes you further afield (to home page of R. E. Pollock).