Features of collisionless turbulence in the intracluster medium from simulated Faraday rotation maps - II. The effects of instabilities feedback

Author(s)

Santos-Lima, R. ; Dal Pino, E. M. de Gouveia ; Falceta-Goncalves, D. A. ; Nakwacki, M. S. ; Kowal, G.

• Document type: Journal article
• Source: Monthly Notices of the Royal Astronomical Society; v. 465, n. 4, p. 4866-4871, MAR 2017.
• Web of Science Citations: 5

Abstract

Statistical analysis of Faraday rotation measure (RM) maps of the intracluster medium (ICM) of galaxy clusters provides a unique tool to evaluate some spatial features of the magnetic fields there. Its combination with numerical simulations of magnetohydrodynamic (MHD) turbulence allows the diagnosis of the ICM turbulence. Being the ICM plasma weakly collisional, the thermal velocity distribution of the particles naturally develops anisotropies as a consequence of the large-scale motions and the conservation of the magnetic moment of the charged particles. A previous study (Paper I) analysed the impact of large-scale thermal anisotropy on the statistics of RM maps synthesized from simulations of turbulence; these simulations employed a collisionless MHD model that considered a tensor pressure with uniform anisotropy. In this work, we extend that analysis to a collisionless MHD model in which the thermal anisotropy develops according to the conservation of the magnetic moment of the thermal particles. We also consider the effect of anisotropy relaxation caused by the microscale mirror and firehose instabilities. We show that if the relaxation rate is fast enough to keep the anisotropy limited by the threshold values of the instabilities, the dispersion and power spectrum of the RM maps are indistinguishable from those obtained from collisional MHD. Otherwise, there is a reduction in the dispersion and steepening of the power spectrum of the RM maps (compared to the collisional case). Considering the first scenario, the use of collisional MHD simulations for modelling the RM statistics in the ICM becomes better justified. (AU)

• 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 Opportunities: Scholarships in Brazil - Post-Doctoral
• 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 Opportunities: Special Projects
• FAPESP's process: 13/18815-0 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources
• Grantee: Grzegorz Kowal
• Support Opportunities: Scholarships in Brazil - Young Researchers
• FAPESP's process: 13/04073-2 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources
• Grantee: Grzegorz Kowal
• Support Opportunities: Research Grants - Young Investigators Grants