Angular Momentum Transport and Particle Acceleration during Magnetorotational Instability in a Kinetic Accretion Disk

TL;DR

This study uses 3D PIC simulations to explore how kinetic MRI in collisionless accretion disks enhances angular momentum transport and accelerates particles, potentially explaining high-energy particles near black holes.

Contribution

It demonstrates the dual role of plasma pressure anisotropy in suppressing and promoting magnetic reconnection, leading to high energy particle acceleration and increased angular momentum transport.

Findings

Kinetic MRI enhances angular momentum transport via Maxwell stress.

Pressure anisotropy influences magnetic reconnection dynamics.

Efficient particle acceleration occurs during reconnection in collisionless disks.

Abstract

Angular momentum transport and particle acceleration during the magnetorotational instability (MRI) in a collisionless accretion disk are investigated using three-dimensional particle-in-cell (PIC) simulation. We show that the kinetic MRI can provide not only high energy particle acceleration but also enhancement of angular momentum transport. We find that the plasma pressure anisotropy inside the channel flow with $p_{\|} > p_{\perp}$ induced by active magnetic reconnection suppresses the onset of subsequent reconnection, which in turn leads to high magnetic field saturation and enhancement of Maxwell stress tensor of angular momentum transport. Meanwhile, during the quiescent stage of reconnection the plasma isotropization progresses in the channel flow, and the anisotropic plasma with $p_{\perp} > p_{\|}$ due to the dynamo action of MRI outside the channel flow contributes to rapid reconnection and strong particle acceleration. This efficient particle acceleration and enhanced angular momentum transport in a collisionless accretion disk may explain the origin of high energy particles observed around massive black holes.