The role of pressure anisotropy in the turbulent intracluster medium

TL;DR

This paper investigates how pressure anisotropy influences magnetic fluctuations and turbulence in the collisionless plasma of the intracluster medium, using numerical simulations within a kinetic MHD framework.

Contribution

It introduces a kinetic MHD approach to study pressure anisotropy effects on turbulence in the ICM, comparing results with traditional MHD models.

Findings

Pressure anisotropy significantly affects magnetic fluctuation growth.

Kinetic MHD results differ from classical MHD predictions.

Pressure anisotropy impacts observable turbulence properties.

Abstract

In low-density plasma environments, such as the intracluster medium (ICM), the Larmour frequency is much larger than the ion-ion collision frequency. In such a case, the thermal pressure becomes anisotropic with respect to the magnetic field orientation and the evolution of the turbulent gas is more correctly described by a kinetic approach. A possible description of these collisionless scenarios is given by the so-called kinetic magnetohydrodynamic (KMHD) formalism, in which particles freely stream along the field lines, while moving with the field lines in the perpendicular direction. In this way a fluid-like behavior in the perpendicular plane is restored. In this work, we study fast growing magnetic fluctuations in the smallest scales which operate in the collisionless plasma that fills the ICM. In particular, we focus on the impact of a particular evolution of the pressure anisotropy and its implications for the turbulent dynamics of observables under the conditions prevailing in the ICM. We present results from numerical simulations and compare the results which those obtained using an MHD formalism.