Pressure-Strain Interaction as the Energy Dissipation Estimate in Collisionless Plasma

TL;DR

This study demonstrates that pressure-strain interaction accurately estimates energy dissipation in collisionless plasma, validated through kinetic simulations, challenging traditional reliance on inertial range-based methods.

Contribution

It provides a direct validation of pressure-strain interaction as the primary measure of energy dissipation in collisionless plasma using kinetic simulations.

Findings

Pressure-strain interaction tracks internal energy increase and temperature enhancement.

Incompressive pressure-strain dominates over compressive in all simulations.

Pressure-strain balances dissipation rate at kinetic scales regardless of scale separation.

Abstract

The dissipative mechanism in weakly collisional plasma is a topic that pervades decades of studies without a consensus solution. We compare several energy dissipation estimates based on energy transfer processes in plasma turbulence and provide justification for the pressure-strain interaction as a direct estimate of the energy dissipation rate. The global and scale-by-scale energy balances are examined in 2.5D and 3D kinetic simulations. We show that the global internal energy increase and the temperature enhancement of each species are directly tracked by the pressure-strain interaction. The incompressive part of the pressure-strain interaction dominates over its compressive part in all simulations considered. The scale-by-scale energy balance is quantified by scale filtered Vlasov-Maxwell equations, a kinetic plasma approach, and the lag dependent von K\'arm\'an-Howarth equation, an approach based on fluid models. We find that the energy balance is exactly satisfied across all scales, but the lack of a well-defined inertial range influences the distribution of the energy budget among different terms in the inertial range. Therefore, the widespread use of the Yaglom relation to estimating dissipation rate is questionable in some cases, especially when the scale separation in the system is not clearly defined. In contrast, the pressure-strain interaction balances exactly the dissipation rate at kinetic scales regardless of the scale separation.