Revisiting compressible and incompressible pressure-strain interaction in kinetic plasma turbulence

In this study, we revisit the pressure-strain interaction in kinetic turbulence, and in particular we re-examine the decomposition of pressure-strain interaction into compressive and incompressive parts. The pressure dilatation ingredient is clearly due to plasma compressions, but here using kinetic particle-in-cell (PIC) simulations of plasma turbulence, it is demonstrated that the remaining anisotropic part, often called Pi-D, also contains contributions due to compressive, non solenoidal velocities of the particle species. The compressive Pi-D can play a significant role in systems with low plasma $\beta$ even if the system starts with small density variations. The compressive ingredient of Pi-D is found to be anticorrelated with both incompressive Pi-D and pressure dilatation.