Particle-Gas Hybrid Schemes in the PLUTO Code

Hybrid codes treating composite systems made up of fluid and particle components are becoming increasing more popular in order to address multiple scale in complex astrophysical environments. Here we review some recent additions to the PLUTO code consisting of three flexible particle physics implementations targeting i) cosmic ray particles, ii) sub-grid electron acceleration and emission from high-energy astrophysical environments and iii) dust grains in protoplanetary disks. While the fluid equations are generally solved using standard finite-volume techniques, integration of particles as well as their feedback onto the gas is treated using standard techniques borrowed from Particle-In-Cell (PIC) frameworks. Some novel numerical benchmarks, not discussed in the original method papers, are also presented.