Large-scale Compression Acceleration during Magnetic Reconnection in a Low-$\beta$ Plasma

Abstract

In solar flares and other astrophysical systems, a major challenge for solving particle acceleration problem associated with magnetic reconnection is the enormous scale separation between kinetic scales and observed reconnection scale. Because of this, it has been difficult to draw any definite conclusions by just using kinetic simulations. Particle acceleration model that solves energetic particle transport equation can capture the main acceleration physics found in kinetic simulations, and thus provide a practical way to make observable predictions and directly compare model results with observations. Here we study compression particle acceleration in magnetic reconnection by solving Parker (diffusion-advection) transport equation using velocity and magnetic fields from two-dimensional high-Lundquist-number magnetohydrodynamics (MHD) simulations of a low-$\beta$ reconnection layer. We show that the compressible reconnection layer can give significant particle acceleration, leading to the formation of power-law particle energy distributions. We analyze the acceleration rate and find that the acceleration in the reconnection layer is a mixture of first order and second order Fermi processes. When including a guide field, we find the spectrum becomes steeper and both the power-law cutoff energy and maximum particle energy decrease as plasma becomes less compressible. This model produces 2D particle distribution that one can use to generate radiation map and directly compare with solar flare observations. This provides a framework to explain particle acceleration at large-scale astrophysical reconnection sites, such as solar flares.

26 pages, 8 figures, ApJ

References in corpus (23)

• Athena: A New Code for Astrophysical MHD
• Instability of current sheets and formation of plasmoid chains
• Formation of Hard Power-laws in the Energetic Particle Spectra Resulting from Relativistic Magnetic Reconnection
• The Mechanisms of Electron Heating and Acceleration during Magnetic Reconnection
• Microwave and Hard X-Ray Observations of the 2017 September 10 Solar Limb Flare
• General Theory of the Plasmoid Instability
• Turbulent Magnetohydrodynamic Reconnection Mediated by the Plasmoid Instability
• Role of magnetic reconnection in MHD turbulence
• A Hitch-hiker's Guide to Stochastic Differential Equations: Solution Methods for Energetic Particle Transport in Space Physics and Astrophysics
• Collisionless Reconnection in Magnetohydrodynamic and Kinetic Turbulence
• Disruption of Alfvénic turbulence by magnetic reconnection in a collisionless plasma
• Magnetohydrodynamic turbulence mediated by reconnection
• Statistics of Reconnection-Driven Turbulence
• Electron Power-Law Spectra in Solar and Space Plasmas
• Stochastic Acceleration in Turbulent Electric Fields Generated by 3-D Reconnection
• The roles of fluid compression and shear in electron energization during magnetic reconnection
• Drift Turbulence, Particle Transport, and Anomalous Dissipation at the Reconnecting Magnetopause
• The Mechanisms of Electron Acceleration During Multiple X Line Magnetic Reconnection with a Guide Field
• Magnetohydrodynamic Turbulence in the Plasmoid-Mediated Regime
• Hard X-Ray Emission from Partially Occulted Solar Flares: RHESSI Observations in Two Solar Cycles
• The acceleration of high-energy protons at coronal shocks: the effect of large-scale streamer-like magnetic field structures
• Influence of tearing instability on magnetohydrodynamic turbulence
• Plasma compression in magnetic reconnection regions in the solar corona

Cited by in corpus (28)

• Measurement of magnetic field and relativistic electrons along a solar flare current sheet
• Magnetic reconnection in the era of exascale computing and multiscale experiments
• Formation of Power-law Electron Energy Spectra in Three-dimensional Low-$\beta$ Magnetic Reconnection
• Recent Progress on Particle Acceleration and Reconnection Physics during Magnetic Reconnectionin the Magnetically-dominated Relativistic Regime
• Determining the Dominant Acceleration Mechanism during Relativistic Magnetic Reconnection in Large-scale Systems
• Magnetic Reconnection During the Post-Impulsive Phase of a Long-Duration Solar Flare: Bi-Directional Outflows as a Cause of Microwave and X-ray Bursts
• Microwave Spectral Imaging of an Erupting Magnetic Flux Rope: Implications for the Standard Solar Flare Model in Three Dimensions
• Magnetic Energy Release, Plasma Dynamics, and Particle Acceleration during Relativistic Turbulent Magnetic Reconnection
• A computational model for exploring particle acceleration during reconnection in macro-scale systems
• The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares
• Particle Injection and Nonthermal Particle Acceleration in Relativistic Magnetic Reconnection
• The Acceleration of Charged Particles and Formation of Power-law Energy Spectra in Nonrelativistic Magnetic Reconnection
• Radiation and Polarization Signatures from Magnetic Reconnection in Relativistic Jets--I. A Systematic Study
• Exploring the acceleration mechanisms for particle injection and power-law formation during trans-relativistic magnetic reconnection
• Energetic Electron Distribution of the Coronal Acceleration Region: First results from Joint Microwave and Hard X-ray Imaging Spectroscopy
• Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10 Solar Flare
• Particle acceleration in kinetic simulations of non-relativistic magnetic reconnection with different ion-electron mass ratio
• Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares: Connecting Loop-top and Footpoint Hard X-Ray Sources
• Large-Scale Parallel Electric Fields and Return Currents in a Global Simulation Model
• The Acceleration of Energetic Particles at Coronal Shocks and Emergence of a Double Power Law Feature in Particle Energy Spectra
• Dynamical modulation of solar flare electron acceleration due to plasmoid-shock interactions in the looptop region
• First-Principle Prediction of X-ray Polarization from Magnetic Reconnection in High-Frequency BL Lacs
• Double-power-law feature of energetic particles accelerated at coronal shocks
• A model of double coronal hard X-ray sources in solar flares
• Spectral Power-law Formation by Sequential Particle Acceleration in Multiple Flare Magnetic Islands
• Particle Acceleration in Magnetic Reconnection with Ad hoc Pitch-angle Scattering
• Compression Acceleration of Protons and Heavier Ions at the Heliospheric Current Sheet
• Particle injection in three-dimensional relativistic magnetic reconnection