 |
Center for Nonlinear Studies |
Plasmas are commonly referred to as the fourth state of matter and represent 99% of the matter in the universe. They can be very complex and therefore advanced modeling would be required to obtain a better understanding. All plasma models solve the magneto-hydrodynamic (MHD) equations which are a combination of the hydrodynamic equations that describe any fluid flow and Maxwell's equations that describe the behavior of electric and magnetic fields. PIXIE3D is a parallel magneto-hydrodynamic code developed for the study of tokamaks and basic plasma physics such as magnetic reconnection. Magnetic reconnection is an important process in which magnetic field lines can splice different domains, storing and releasing large amounts of energy and can lead to the formation of extremely thin sheets of current. While PIXIE3D is a powerful simulation tool, the plasmas it simulates experience a wide variety of spatial and temporal scales. As a result, a high resolution grid is necessary in order to capture the regions of interest for an accurate solution, which leads to unnecessary calculations in the regions where the plasma does not vary significantly. For example, in a typical plasma simulation resolution of the current sheets is necessary for an accurate solution, but these sheets can be very localized with thicknesses that are less than 1/1000th the domain size. Since this is also a 3d problem, this means that the size of the grid grows as O(n3) where n is the number of gridpoints necessary to achieve the resolution needed for these current sheets. To solve this problem we are working on adding Adaptive Mesh Refinement (AMR) capabilities to PIXIE3D. AMR uses a series of different resolution levels, each level covers part of the domain. As the simulation progresses, the different spatial regions can be refined to change their resolution. This allows the model to use different spatial scales in the different spatial regions of interest to better match the local scale of plasma conditions. We are using a package called SAMRAI (Structured Adaptive Mesh Refinement Applications Infrastructure) for the general AMR routines that will be needed. I will be presenting on the development of an explicit, parallel, Adaptive Mesh Refinement MHD code used for the modeling of plasmas.
Host: Bobby Philip