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Dr. Allard Jan van Marle visited ABBL and iTHEMS this week from his home institute of UNIST in South Korea. On Monday, June 17, he gave a seminar about his work in astrophysics, on particle acceleration and particle-shock interactions. This is a very difficult topic to study because of the very different scales (length, time, and energy) involved. Low-energy electrons and ions create the magnetic field turbulence that lets particle acceleration take place, so numerical simulations should resolve their motion. But accelerated particles have energies orders of magnitude higher, which means the numerical grid must be much larger to track them. Dr. van Marle presented a new numerical method that partially resolves this tension. This "particle in [MHD] cell" code averages out the majority of the low-energy electrons/ions, freeing up computational resources to track the higher-energy particles that are of more interest to most astrophysicists. Shock fronts are everywhere in the universe, but they come in a large variety of speeds, sizes, and locations. The work presented by Dr. van Marle will help to determine how (or if) all of these different shocks behave as natural particle accelerators.