Limits on the ion temperature anisotropy in the turbulent intracluster medium

Author(s)

Santos-Lima, R. ; Yan, H. ; de Gouveia Dal Pino, E. M. ; Lazarian, A.

• Document type: Journal article
• Source: Monthly Notices of the Royal Astronomical Society; v. 460, n. 3, p. 2492-2504, AUG 11 2016.
• Web of Science Citations: 4

Abstract

Turbulence in the weakly collisional intracluster medium (ICM) of galaxies is able to generate strong thermal velocity anisotropies in the ions (with respect to the local magnetic field direction), if the magnetic moment of the particles is conserved in the absence of Coulomb collisions. In this scenario, the anisotropic pressure magnetohydrodynamic (AMHD) turbulence shows a very different statistical behaviour from the standard MHD one and is unable to amplify seed magnetic fields. This is in contrast to previous cosmological MHD simulations that are successful in explaining the observed magnetic fields in the ICM. On the other hand, temperature anisotropies can also drive plasma instabilities that can relax the anisotropy. This work aims to compare the relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasi-linear theory to estimate the ion scattering rate resulting from the parallel firehose, mirror and ion-cyclotron instabilities, for a set of plasma parameters resulting from AMHD simulations of the turbulent ICM. We show that the ICM turbulence can sustain only anisotropy levels very close to the instability thresholds. We argue that the AMHD model that bounds the anisotropies at the marginal stability levels can describe the Alfv,nic turbulence cascade in the ICM. (AU)

• FAPESP's process: 13/10559-5 - Investigation of high energy and plasma astrophysics phenomena: theory, numerical simulations, observations, and instrument development for the Cherenkov Telescope Array (CTA)
• Grantee: Elisabete Maria de Gouveia Dal Pino
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 13/15115-8 - Study of collisionless plasma effects: application to the turbulent intracluster medium of galaxies
• Grantee: Reinaldo Santos de Lima
• Support type: Scholarships in Brazil - Post-Doctorate