Spontaneous large scale momentum exchange by microinstabilities: an analogy between tokamaks and space plasmas

TL;DR

This paper proposes that microinstabilities can spontaneously generate large-scale momentum exchange in plasmas, drawing analogies between tokamaks and space environments, supported by kinetic simulations showing velocity shear formation.

Contribution

It introduces a novel analogy between tokamak and space plasma dynamics, demonstrating spontaneous momentum exchange via microinstabilities through kinetic PIC simulations.

Findings

Spontaneous velocity shear develops in plasma simulations.

Microscopic fluctuations are confined to the plasma edge.

Momentum spreads across the entire plasma system.

Abstract

Based on a recent theory (Coppi, Nuclear Fusion, 42, 1, 2002) of spontaneous toroidal rotation in tokamaks (Lee et al, Phys Rev Lett, 91, 205003, 2003) and in astrophysical accretion disks, we propose that an analogous process could be at play also in the Earth space environment. We use fully kinetic PIC simulations to study the evolution of drift instabilities and we show that indeed a macroscopic velocity shear is generated spontaneously in the plasma. As in tokamaks, the microscopic fluctuations remain limited to the edge of the plasma channel but the momentum spreads over the whole macroscopic system.