Nonlinear Dynamics of Mirror Instability Revisited

Pokhotelov, O. A.; Sagdeev, R. Z.; Balikhin, M. A.; Fedun, V.N.; Dudnikova, G. I.

doi:10.1063/1.3533179

Cited by 1 publication

(1 citation statement)

References 12 publications

(17 reference statements)

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“…δB y shows a mixture of the nearly parallel modes, plus subdominant oblique modes, which are consistent with the presence of mirror modes. Indeed, these modes mainly contribute to the δB components parallel to the plane of the simulation (they show no δB z component), which is in line with the expectation that δB of the mirror modes is nearly perpendicular to k ×B (Pokhotelov et al 2004).…”

Section: D 1dsupporting

confidence: 87%

Stochastic Ion Acceleration by the Ion-cyclotron Instability in a Growing Magnetic Field

Ley

Riquelme

Sironi

et al. 2019

ApJ

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Using 1D and 2D particle-in-cell (PIC) simulations of a plasma with a growing magnetic field B, we show that ions can be stochastically accelerated by the ion-cyclotron (IC) instability. As B grows, an ion pressure anisotropy p ⊥,i > p ||,i arises, due to the adiabatic invariance of the ion magnetic moment (p ||,i and p ⊥,i are the ion pressures parallel and perpendicular to B). When initially β i = 0.5 (β i ≡ 8πp i /|B| 2 , where p i is the ion isotropic pressure), the pressure anisotropy is limited mainly by inelastic pitch-angle scattering provided by the IC instability, which in turn produces a non-thermal tail in the ion energy spectrum. After B is amplified by a factor ∼ 2.7, this tail can be approximated as a power-law of index ∼ 3.4 plus two non-thermal bumps, and accounts for 2 − 3% of the ions and ∼ 18% of their kinetic energy. On the contrary, when initially β i = 2, the ion scattering is dominated by the mirror instability and the acceleration is suppressed. This implies that efficient ion acceleration requires that initially β i 1. Although we focus on cases where B is amplified by plasma shear, we check that the acceleration occurs similarly if B grows due to plasma compression. Our results are valid in a sub-relativistic regime where the ion thermal energy is ∼ 10% of the ion rest mass energy. This acceleration process can thus be relevant in the inner region of low-luminosity accretion flows around black holes.

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Section: D 1dsupporting

confidence: 87%