The Effect of Thermal Pressure on Collisionless Magnetic Reconnection Rate

Abstract

Modeling collisionless magnetic reconnection rate is an outstanding challenge in basic plasma physics research. While the seemingly universal rate of an order $\mathcal{O}(0.1)$ is often reported in the low-$\beta$ regime, it is not clear how reconnection rate scales with a higher plasma $\beta$. Due to the complexity of the pressure tensor, the available reconnection rate model is limited to the low plasma-$\beta$ regime, where the thermal pressure is arguably negligible. However, the thermal pressure effect becomes important when $\beta \gtrsim \mathcal{O}(1)$. Using first-principle kinetic simulations, we show that both the reconnection rate and outflow speed drop as $\beta$ gets larger. A simple analytical framework is derived to take account of the self-generated pressure anisotropy and pressure gradient in the force-balance around the diffusion region, explaining the varying trend of key quantities and reconnection rates in these simulations with different $\beta$. The predicted scaling of the normalized reconnection rate is $\simeq \mathcal{O}(0.1/\sqrt{{\beta }_{i0}})$ in the high $\beta$ limit, where ${\beta }_{i0}$ is the ion $\beta$ of the inflow plasma.

arXiv comment19 pages, 7 figures, accepted for publication in ApJ

References in corpus (21)

• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• Cluster Magnetic Fields
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• Dissipation of the sectored heliospheric magnetic field near the heliopause: a mechanism for the generation of anomalous cosmic rays
• Electron Acceleration by Multi-Island Coalescence
• The Mechanisms of Electron Heating and Acceleration during Magnetic Reconnection
• Why does steady-state magnetic reconnection have a maximum local rate of order 0.1?
• Turbulence, magnetic fields and plasma physics in clusters of galaxies
• A Review of the 0.1 Reconnection Rate Problem
• Reduction of Ion Heating During Magnetic Reconnection by Large-Scale Effective Potentials
• Nonthermally Dominated Electron Acceleration during Magnetic Reconnection in a Low-beta Plasma
• Energy Release and Particle Acceleration in Flares: Summary and Future Prospects
• The structure of the magnetic reconnection exhaust boundary
• The Origin of the Magnetic Fields of the Universe: The Plasma Astrophysics of the Free Energy of the Universe
• The effects of plasma beta and anisotropy instabilities on the dynamics of reconnecting magnetic fields in the heliosheath
• 3D Magnetic Reconnection with a spatially confined X-line extent -- Implications for Dipolarizing Flux Bundles and the Dawn-Dusk Asymmetry
• Particle acceleration in kinetic simulations of non-relativistic magnetic reconnection with different ion-electron mass ratio
• The Reduction of Magnetic Reconnection Outflow Jets to Sub-Alfvénic Speeds
• The effects of strong temperature anisotropy on the kinetic structure of collisionless slow shocks and reconnection exhausts. Part II: Theory
• Scaling of magnetic reconnection with a limited x-line extent
• Onset of magnetic reconnection in a collisionless, high-beta plasma

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• Efficient Nonthermal Ion and Electron Acceleration Enabled by the Flux-Rope Kink Instability in 3D Nonrelativistic Magnetic Reconnection
• Radiative Signatures of Magnetic Reconnection: An Approach to Remote Probing of Reconnection Dynamics