Abstract
This work, which extends Squire et al (Astrophys. J. Lett. 2016 830 L25), explores the effect of self-generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality plasmas. Such anisotropies lead to stringent limits on the amplitude of magnetic perturbations in high-β plasmas, above which a fluctuation can destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, ‘interrupting’ the wave and stopping its oscillation. These effects are explored in detail in the collisionless and weakly collisional ‘Braginskii’ regime, for both standing and traveling waves. The focus is on simplified models in one dimension, on scales much larger than the ion gyroradius. The effect has interesting implications for the physics of magnetized turbulence in the high-β conditions that are prevalent in many astrophysical plasmas.
Highlights
17 May 20172016 830 L25), explores the effect of selfauthor(s) and the title of the work, journal citation generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality and DOI
In this paper, we derive and discuss stringent nonlinear limits on the amplitude of shear-Alfvén (SA) fluctuations in weakly collisional plasmas
What is the cause of such dramatic nonlinear behavior, even in regimes where linear physics might appear to be applicable? As we explain, the effect depends on the development of pressure anisotropy—i.e., a pressure tensor that differs in the directions perpendicular and parallel to the magnetic field
Summary
2016 830 L25), explores the effect of selfauthor(s) and the title of the work, journal citation generated pressure anisotropy on linearly polarized shear-Alfvén fluctuations in low-collisionality and DOI. Such anisotropies lead to stringent limits on the amplitude of magnetic perturbations in high-β plasmas, above which a fluctuation can destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, ‘interrupting’ the wave and stopping its oscillation. These effects are explored in detail in the collisionless and weakly collisional ‘Braginskii’. The effect has interesting implications for the physics of magnetized turbulence in the high-β conditions that are prevalent in many astrophysical plasmas
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