Visualization of Flow Properties in Mantle Convection: Understanding Homogenization in CitcomS

Understanding the complex behavior of mixing in the Earth's mantle remains a challenge in geoscience. One means to both interpret mantle flow models and enable comparisons with observations of the scale of mantle heterogeneity is by assessing the homogenization of passive tracers in models. Computer simulations of mantle mixing often yield both divergent and convergent regions which homogenize the mantle, as well as isolated pockets where almost no mixing occurs. Analyzing and understanding this complex behavior requires appropriate simulation and visualization tools. To reach this goal, we introduce new visualization techniques that allow geophysicists to effectively analyze this simulation data. Our visualization tool takes, as input, the velocity field and tracers generated by CitcomS, a well-established finite-element model of mantle convection in a spherical shell. By visualization of particle statistics, e.g. average traveled distance of tracers inside a pre-defined region, we provide a better understanding of homogenization in the mixing process. To reduce the amount of data generated by CitcomS, we only compute a few tracers during simulation time compared to the overall size of the data set. Statistics defined on this set of tracers allow an initial low detail analysis of the flow field while providing only limited preliminary insights into the data set. For further refinement in a specific region of interest we offer capabilities to locally add and integrate new tracers directly inside the visualization tool, facilitating interactive resolution control. This results in more detailed local statistics and is faster than resimulating tracers inside CitcomS by restarting the complete simulation run. Furthermore, we take well-known concepts from computer graphics to reduce visual clutter and help focus on a specific region of interest, such as slicing and volume rendering. Our results are suitable to gain a better understanding about homogenization of mixing processes in mantle convection. More specifically, we tested how homogeneous mixing between several mantle layers is. Further, by visualization of tracer paths some insight into the properties of the flow field is given. Using these techniques, geophysicists are able to test their hyphotheses regarding scales of mantle heterogeneity.