Fully kinetic simulations of magnetorotational turbulence in a three-dimensional shearing box

The magnetorotational instability (MRI) is a fundamental process driving the dynamics of accretion disks. The MRI amplifies magnetic fields and can promote angular-momentum transport, nonthermal particle acceleration, and differential electron-ion heating by sustaining a turbulent cascade from the macroscopic (fluid) to the microscopic (kinetic) scales of plasmas in such disks. However, a complete understanding of MRI-driven turbulence in the collisionless regime is still missing, due to a lack of fully kinetic, three-dimensional (3D) models capturing the nonlinear MRI dynamics. Here, we present the first large-scale, 3D, Particle-in-Cell (PIC) simulations of MRI-driven turbulence based on a novel shearing-box formulation. Our large-scale simulations reproduce the fluid (i.e. mesoscale) behavior expected from MHD numerical experiments; in addition, our PIC approach allows us to quantify kinetic effects that cannot be captured in MHD, such as particle acceleration, enhanced angular-momentum transport due to pressure anisotropy, collisionless plasma heating, etc. Although here we focus on pair plasmas, our work paves the way for future electron-ion simulations, which will advance our understanding of observationally targeted accretion flows such as those surrounding M87* and SgrA*.