Passive convection of density fluctuations in the local interstellar medium

We have developed a time-dependent three-dimensional model of isotropic, adiabatic, and compressible magnetohydrodynamic plasma to understand nonlinear cascades of density fluctuations in local interstellar medium. Our simulations, describing the evolution of initial supersonic, super Alfvenic plasma modes, indicate that nonlinear interactions lead to the damping of plasma fluctuations. During the decay process, turbulent cascades are governed predominantly by the Alfvenic modes and velocity field fluctuations evolve towards a state characterized by near incompressibility. Consequently, the density field is advected passively by the velocity field. Our findings demonstrate that density fluctuations observed in the interstellar medium are passively convected by the background velocity field.