Density jump as a function of magnetic field strength for parallel collisionless shocks in pair plasmas

Abstract

Collisionless shocks follow the Rankine-Hugoniot jump conditions to a good approximation. However, for a shock propagating parallel to a magnetic field, magnetohydrodynamics states that the shock properties are independent of the field strength, whereas recent Particle-in-Cell simulations reveal a significant departure from magnetohydrodynamics behavior for such shocks in the collisionless regime. This departure is found to be caused by a field-driven anisotropy in the downstream pressure, but the functional dependence of this anisotropy on the field strength is yet to be determined. Here, we present a non-relativistic model of the plasma evolution through the shock front, allowing for a derivation of the downstream anisotropy in terms of the field strength. Our scenario assumes double adiabatic evolution of a pair plasma through the shock front. As a result, the perpendicular temperature is conserved. If the resulting downstream is firehose stable, then the plasma remains in this state. If unstable, it migrates towards the firehose stability threshold. In both cases, the conservation equations, together with the relevant hypothesis made on the temperature, allows a full determination of the downstream anisotropy in terms of the field strength.

arXiv commentTo appear in Journal of Plasma Physics, 16 pages, 7 figures

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Cited by in corpus (12)

• Long-term Evolution of Relativistic Unmagnetized Collisionless Shocks
• Density jump as a function of magnetic field for collisionless shocks in pair plasmas: the perpendicular case
• Density jump as a function of magnetic field for switch-on collisionless shocks in pair plasmas
• Modified jump conditions for parallel collisionless shocks
• Density jump for oblique collisionless shocks in pair plasmas: allowed solutions
• Density jump as a function of magnetic field strength for parallel collisionless shocks with anisotropic upstream pressure
• Bridging the gap between collisional and collisionless shock waves
• Density jump as a function of magnetic field strength for perpendicular collisionless shocks with anisotropic upstream pressure
• Parallel Collisionless Shocks in strongly Magnetized Electron-Ion Plasma. I. Temperature anisotropies
• Building a weak shockwave from linear modes
• Particle trajectories in Weibel filaments: influence of external field obliquity and chaos
• Kinetic Simulations of Strongly-Magnetized Parallel Shocks: Deviations from MHD Jump Conditions