Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence

Montag, P.; Egedal, J.; Lichko, Emily; Wetherton, Blake

doi:10.1063/1.4985302

Cited by 38 publications

(44 citation statements)

References 24 publications

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“…These results differ from some previous modeling works, in which the authors assumed that the reconnection layer is incompressible (Bian & Kontar 2013;Drake et al 2013). Compressibility has been emphasized in recent models of particle energization in magnetic reconnection (le Roux et al 2015;Montag et al 2017). This work provides the first quantitative evaluation of the role of compressibility in fully kinetic simulations.…”

Section: Discussioncontrasting

confidence: 82%

“…This work provides the first quantitative evaluation of the role of compressibility in fully kinetic simulations. Also, the plasma energization described by Equation (9) is consistent with the general analytical theory by Montag et al (2017) (see the Appendix) based on double-adiabatic assumptions.…”

Section: Discussionsupporting

confidence: 81%

“…Note that le Roux et al (2015) have shown similar energization terms (Equation (13) in their paper) by using the guiding-center drift kinetic equation, but they did not specifically point out the role of pressure anisotropy and fluid shear. Since current analysis employs the same two assumptions as the CGL closure, i.e., neglecting heat fluxes and assuming magnetized particles, the plasma energization shown in Equation (9) is consistent with other theories based on these assumptions (Montag et al 2017; see the Appendix). We argue that v E is a proper choice of perpendicular plasma flow for studying particle energization by fluid motions.…”

Section: Compressional Energization and Shear Energizationsupporting

confidence: 60%

“…By assuming that particles are magnetized and neglecting the heat flux (Chew et al 1956), Montag et al (2017) showed that the energization for a single energetic particle is [their…”

Section: Appendixmentioning

confidence: 99%

“…Drury (2012) treated the acceleration of particles in reconnection similar to the diffusive shock acceleration and showed that compression is important for driving particle acceleration. Zank et al (2014), le Roux et al (2015, and Montag et al (2017) have pointed out that the compression effect may be important for particle energization in reconnection regions. These appear to be in contradiction with some previous theories that assume the reconnection layer is incompressible(e.g., Drake et al 2006Drake et al , 2013; see also the discussion in de Gouveia Dal Pino & Kowal 2015).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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

Guo

et al. 2018

ApJ

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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 sufficiently 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.

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Section: Discussioncontrasting

confidence: 82%

Section: Discussionsupporting

confidence: 81%

Section: Compressional Energization and Shear Energizationsupporting

confidence: 60%

“…By assuming that particles are magnetized and neglecting the heat flux (Chew et al 1956), Montag et al (2017) showed that the energization for a single energetic particle is [their…”

Section: Appendixmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Guo

et al. 2018

ApJ

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Particle Acceleration by Magnetic Reconnection in Geospace

Oka,

Birn,

Egedal

et al. 2023

Space Sci Rev

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Particles are accelerated to very high, non-thermal energies during explosive energy-release phenomena in space, solar, and astrophysical plasma environments. While it has been established that magnetic reconnection plays an important role in the dynamics of Earth’s magnetosphere, it remains unclear how magnetic reconnection can further explain particle acceleration to non-thermal energies. Here we review recent progress in our understanding of particle acceleration by magnetic reconnection in Earth’s magnetosphere. With improved resolutions, recent spacecraft missions have enabled detailed studies of particle acceleration at various structures such as the diffusion region, separatrix, jets, magnetic islands (flux ropes), and dipolarization front. With the guiding-center approximation of particle motion, many studies have discussed the relative importance of the parallel electric field as well as the Fermi and betatron effects. However, in order to fully understand the particle acceleration mechanism and further compare with particle acceleration in solar and astrophysical plasma environments, there is a need for further investigation of, for example, energy partition and the precise role of turbulence.

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Multi-scale simulations of particle acceleration in astrophysical systems

Marcowith

Ferrand

Grech

et al. 2020

Living Rev Comput Astrophys

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This review aims at providing an up-to-date status and a general introduction to the subject of the numerical study of energetic particle acceleration and transport in turbulent astrophysical flows. The subject is also complemented by a short overview of recent progresses obtained in the domain of laser plasma experiments. We review the main physical processes at the heart of the production of a non-thermal distribution in both Newtonian and relativistic astrophysical flows, namely the first and second order Fermi acceleration processes. We also discuss shock drift and surfing acceleration, two processes important in the context of particle injection in shock acceleration. We analyze with some details the particle-in-cell (PIC) approach used to describe particle kinetics. We review the main results obtained with PIC simulations in the recent years concerning particle acceleration at shocks and in reconnection events. The review discusses the solution of Fokker–Planck problems with application to the study of particle acceleration at shocks but also in hot coronal plasmas surrounding compact objects. We continue by considering large scale physics. We describe recent developments in magnetohydrodynamic (MHD) simulations. We give a special emphasis on the way energetic particle dynamics can be coupled to MHD solutions either using a multi-fluid calculation or directly coupling kinetic and fluid calculations. This aspect is mandatory to investigate the acceleration of particles in the deep relativistic regimes to explain the highest cosmic ray energies.

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Impact of compressibility and a guide field on Fermi acceleration during magnetic island coalescence

Cited by 38 publications

References 24 publications

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

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

Particle Acceleration by Magnetic Reconnection in Geospace

Multi-scale simulations of particle acceleration in astrophysical systems

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