Astroplasmas Seminar

Next seminar 

Monday, June 17th, 2024, 3:00 pm, Dome room, Peyton Hall (Please note the unusual time)

Title: Fully kinetic shearing box simulations of magnetorotational instability in electron-ion plasma

Speaker: Evgeny Gorbunov (KU Leuven)

Abstract: Accretion disks are widely appearing in the universe around massive compact objects such as black holes (BHs), and often consist of relativistically hot, radiative electron-ion plasma in a turbulent state. Global general relativistic magnetohydrodynamics (GRMHD) has been widely and successfully employed to study the global structure of accretion disks, as well as to interpret recent observational data obtained by Event Horizon Telescope (EHT) collaboration. However, it is commonly accepted that low-luminosity targets of EHT are essentially collisionless, with the lack of Coulomb interactions between ions and electrons potentially leading to a two-temperature state of the plasma. The interpretation of observations via GRMHD simulations, which is dependent on the temperature ratio between ions and electrons determined by kinetic physics, is therefore fundamentally limited. Thus, it is critical to more accurately determine the ion-to-electron heating ratio. To improve current existing heating ratio prescriptions and account for a collisionless regime, the kinetic particle-in-cell (PIC) approach is essential to model plasma around BHs. To keep first-principles simulations computationally accessible, we propose a novel shearing-box [1,2] approach, in which only a small region within the accretion disk is modelled. The primary driver for turbulence in this case is the magnetorotational instability (MRI), which significantly amplifies magnetic fields and injects energy at large scales, which can cascade and energize particles. Using this approach, we aim to provide a more accurate prescription for ion-electron heating ratios for more precise global simulations in future.