Turbulence driven by AGN activity, cluster mergers and galaxy motion
constitutes an attractive energy source for heating the intracluster medium
(ICM). How this energy dissipates into the ICM plasma remains unclear, given
its low collisionality and high magnetization (precluding viscous heating by
Coulomb processes). Kunz et al. 2011 proposed a viable heating mechanism based
on the anisotropy of the plasma pressure (gyroviscous heating) under ICM
conditions. The present paper builds upon that work and shows that particles
can be gyroviscously heated by large-scale turbulent fluctuations via magnetic
pumping. We study how the anisotropy evolves under a range of forcing
frequencies, what waves and instabilities are generated and demonstrate that
the particle distribution function acquires a high energy tail. For this, we
perform particle-in-cell simulations where we periodically vary the mean
magnetic field $\mathbf{\text{B}}(t)$ . When $\mathbf{\text{B}}(t)$ grows (dwindles), a
pressure anisotropy ${P}_{\perp}>{P}_{\parallel}$ (${P}_{\perp}<{P}_{\parallel}$ )
builds up (${P}_{\perp}$ and ${P}_{\parallel}$ are, respectively, the pressures
perpendicular and parallel to $\mathbf{\text{B}}(t)$ ). These pressure anisotropies
excite mirror (${P}_{\perp}>{P}_{\parallel}$ ) and oblique firehose
(${P}_{\parallel}>{P}_{\perp}$ ) instabilities, which trap and scatter the
particles, limiting the anisotropy and providing a channel to heat the plasma.
The efficiency of this mechanism depends on the frequency of the large-scale
turbulent fluctuations and the efficiency of the scattering the instabilities
provide in their nonlinear stage. We provide a simplified analytical heating
model that captures the phenomenology involved. Our results show that this
process can be relevant in dissipating and distributing turbulent energy at
kinetic scales in the ICM.