The Roles of Fluid Compression and Shear in Electron Energization during Magnetic Reconnection

Particle acceleration in space and astrophysical reconnection sites is an important unsolved problem in studies of magnetic reconnection. Earlier kinetic simulations have identified several acceleration mechanisms that are associated with particle drift motions. Here, we show that, for sufficient large systems, the energization processes due to particle drift motions can be described as fluid compression and shear, and that the shear energization is proportional to the pressure anisotropy of energetic particles. By analyzing results from fully kinetic simulations, we show that the compression energization dominates the acceleration of high-energy particles in reconnection with a weak guide field, and the compression and shear effects are comparable when the guide field is 50\% of the reconnecting component. Spatial distributions of those energization effects reveal that reconnection exhausts, contracting islands, and island merging regions are the three most important regions for compression and shear acceleration. This study connects particle energization by particle guiding-center drift motions with that due to background fluid motions, as in the energetic particle transport theory. It provides foundations for building particle transport models for large-scale reconnection acceleration such as those in solar flares.

[1]  F. Low,et al.  The Boltzmann equation an d the one-fluid hydromagnetic equations in the absence of particle collisions , 1956, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[2]  Eugene N. Parker,et al.  THE PASSAGE OF ENERGETIC CHARGED PARTICLES THROUGH INTERPLANETARY SPACE , 1965 .

[3]  J. Skilling.  Cosmic Ray Streaming—II EFFECT OF PARTICLES ON ALFVÉN WAVES , 1975 .

[4]  H. Hudson,et al.  Non-thermal processes in large solar flares , 1975 .

[5]  J. Jokipii.  Particle drift, diffusion, and acceleration at shocks , 1982 .

[6]  Roger D. Blandford,et al.  Particle acceleration at astrophysical shocks: A theory of cosmic ray origin , 1987 .

[7]  G. Morfill,et al.  Cosmic-ray viscosity , 1988 .

[8]  F. C. Jones.  The Generalized Diffusion-Convection Equation , 1990 .

[9]  Iku Shinohara,et al.  Suprathermal electron acceleration in magnetic reconnection , 2001 .

[10]  Michael Hesse,et al.  Geospace Environmental Modeling (GEM) magnetic reconnection challenge , 2001 .

[11]  M. Shay,et al.  Production of energetic electrons during magnetic reconnection. , 2003, Physical review letters.

[12]  M. Shay,et al.  Electron acceleration from contracting magnetic islands during reconnection , 2006, Nature.

[13]  Quanming Lu,et al.  The process of electron acceleration during collisionless magnetic reconnection , 2006 .

[14]  P. Pritchett,et al.  Relativistic electron production during guide field magnetic reconnection , 2006 .

[15]  William Daughton,et al.  Fully kinetic simulations of undriven magnetic reconnection with open boundary conditions , 2006 .

[16]  K. Bowers,et al.  Spectral energy transfer and dissipation of magnetic energy from fluid to kinetic scales. , 2007, Physical review letters.

[17]  K. Bowers,et al.  Ultrahigh performance three-dimensional electromagnetic relativistic kinetic plasma simulationa) , 2008 .

[18]  G. Webb,et al.  TIME-DEPENDENT ACCELERATION OF INTERSTELLAR PICKUP IONS AT THE HELIOSPHERIC TERMINATION SHOCK USING A FOCUSED TRANSPORT APPROACH , 2009 .

[19]  Masaaki Yamada,et al.  Magnetic Reconnection in Astrophysical and , 2009 .

[20]  J. Qiu,et al.  A Quantitative Model of Energy Release and Heating by Time-dependent, Localized Reconnection in a Flare with Thermal Loop-top X-ray Source , 2010, 1106.3572.

[21]  A. Caspi,et al.  RHESSI LINE AND CONTINUUM OBSERVATIONS OF SUPER-HOT FLARE PLASMA , 2010, 1105.2839.

[22]  J. Drake,et al.  A MAGNETIC RECONNECTION MECHANISM FOR THE GENERATION OF ANOMALOUS COSMIC RAYS , 2010 .

[23]  Lindsay Glesener,et al.  MEASUREMENTS OF THE CORONAL ACCELERATION REGION OF A SOLAR FLARE , 2010 .

[24]  M. Fujimoto,et al.  ELECTRON ACCELERATION BY MULTI-ISLAND COALESCENCE , 2010, 1004.1154.

[25]  William Daughton,et al.  Large-scale electron acceleration by parallel electric fields during magnetic reconnection , 2011, Nature Physics.

[26]  K. Bowers,et al.  Particle energization in 3D magnetic reconnection of relativistic pair plasmas , 2010, 1005.2435.

[27]  William Daughton,et al.  Role of electron physics in the development of turbulent magnetic reconnection in collisionless plasmas , 2011 .

[28]  L. Drury.  First-order Fermi acceleration driven by magnetic reconnection , 2012, 1201.6612.

[29]  J. Birn,et al.  The role of compressibility in energy release by magnetic reconnection , 2012 .

[30]  William Daughton,et al.  A review of pressure anisotropy caused by electron trapping in collisionless plasma, and its implications for magnetic reconnection , 2013 .

[31]  E. Kontar,et al.  Stochastic acceleration by multi-island contraction during turbulent magnetic reconnection. , 2013, Physical review letters.

[32]  J. Drake,et al.  THE POWER-LAW SPECTRA OF ENERGETIC PARTICLES DURING MULTI-ISLAND MAGNETIC RECONNECTION , 2012, 1210.4830.

[33]  H. Karimabadi,et al.  Regimes of the electron diffusion region in magnetic reconnection. , 2013, Physical review letters.

[34]  S. Krucker,et al.  KAPPA DISTRIBUTION MODEL FOR HARD X-RAY CORONAL SOURCES OF SOLAR FLARES , 2012, 1212.2579.

[35]  S. Krucker,et al.  PARTICLE DENSITIES WITHIN THE ACCELERATION REGION OF A SOLAR FLARE , 2013 .

[36]  Hui Li,et al.  FIRST-ORDER PARTICLE ACCELERATION IN MAGNETICALLY DRIVEN FLOWS , 2014, 1406.6690.

[37]  William Daughton,et al.  Formation of hard power laws in the energetic particle spectra resulting from relativistic magnetic reconnection. , 2014, Physical review letters.

[38]  J. Drake,et al.  The mechanisms of electron heating and acceleration during magnetic reconnection , 2014, 1406.0831.

[39]  S. Krucker,et al.  ELECTRON ENERGY PARTITION IN THE ABOVE-THE-LOOPTOP SOLAR HARD X-RAY SOURCES , 2014 .

[40]  G. Zank,et al.  PARTICLE ACCELERATION VIA RECONNECTION PROCESSES IN THE SUPERSONIC SOLAR WIND , 2014 .

[41]  G. Zank,et al.  A KINETIC TRANSPORT THEORY FOR PARTICLE ACCELERATION AND TRANSPORT IN REGIONS OF MULTIPLE CONTRACTING AND RECONNECTING INERTIAL-SCALE FLUX ROPES , 2015 .

[42]  G. Zank,et al.  DIFFUSIVE SHOCK ACCELERATION AND RECONNECTION ACCELERATION PROCESSES , 2015 .

[43]  G. Werner,et al.  ON THE DISTRIBUTION OF PARTICLE ACCELERATION SITES IN PLASMOID-DOMINATED RELATIVISTIC MAGNETIC RECONNECTION , 2015, 1508.02392.

[44]  Xiaocan Li,et al.  NONTHERMALLY DOMINATED ELECTRON ACCELERATION DURING MAGNETIC RECONNECTION IN A LOW-β PLASMA , 2015, 1505.02166.

[45]  Particle Acceleration by Magnetic Reconnection , 2013, 1302.4374.

[46]  William Daughton,et al.  PARTICLE ACCELERATION AND PLASMA DYNAMICS DURING MAGNETIC RECONNECTION IN THE MAGNETICALLY DOMINATED REGIME , 2015, 1504.02193.

[47]  J. Egedal,et al.  Double layer electric fields aiding the production of energetic flat-top distributions and superthermal electrons within magnetic reconnection exhausts , 2015 .

[48]  M. Bárta,et al.  ELECTRON ACCELERATION BY CASCADING RECONNECTION IN THE SOLAR CORONA. I. MAGNETIC GRADIENT AND CURVATURE DRIFT EFFECTS , 2015, 1504.06486.

[49]  J. Laming,et al.  PLASMA COMPRESSION IN MAGNETIC RECONNECTION REGIONS IN THE SOLAR CORONA , 2016, 1604.07325.

[50]  Can Huang,et al.  THE MECHANISMS OF ELECTRON ACCELERATION DURING MULTIPLE X LINE MAGNETIC RECONNECTION WITH A GUIDE FIELD , 2016, 1602.05315.

[51]  Xiaocan Li,et al.  Particle Acceleration during Magnetic Reconnection in a Low-beta Plasma , 2017 .

[52]  J. Egedal,et al.  Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence , 2017 .