A Brief Review on Particle Acceleration in Multi-island Magnetic Reconnection

Che, H.; Zank, G. P.

doi:10.1088/1742-6596/1332/1/012003

Cited by 7 publications

(4 citation statements)

References 73 publications

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“…From 2D numerical simulations, particle acceleration by multi-island magnetic reconnection was considered plausible for the energization of particles in many explosive phenomena in space and laboratory plasmas. Two dimensional magnetohydrodynamic (MHD) and particle in cell (PIC) simulations analyzing reconnection for mildly relativistic plasma are unable to produce a power-law-shaped energy distribution of particles (Che & Zank 2019;Dahlin 2020).…”

Section: Introductionmentioning

confidence: 99%

Particle heating and acceleration by reconnecting and nonreconnecting current sheets

Sioulas

Isliker

Vlahos

2021

A&A

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In this article, we study the physics of charged particle energization inside a strongly turbulent plasma, where current sheets naturally appear in evolving large-scale magnetic topologies, but they are split into two populations of fractally distributed reconnecting and nonreconnecting current sheets (CS). In particular, we implemented a Monte Carlo simulation to analyze the effects of the fractality and we study how the synergy of energization at reconnecting CSs and at nonreconnecting CSs affects the heating, the power-law high energy tail, the escape time, and the acceleration time of electrons and ions. The reconnecting current sheets systematically accelerate particles and play a key role in the formation of the power-law tail in energy distributions. On the other hand, the stochastic energization of particles through their interaction with nonreconnecting CSs can account for the heating of the solar corona and the impulsive heating during solar flares. The combination of the two acceleration mechanisms (stochastic and systematic), commonly present in many explosive events of various sizes, influences the steady-state energy distribution, as well as the transport properties of the particles in position- and energy-space. Our results also suggest that the heating and acceleration characteristics of ions and electrons are similar, the only difference being the time scales required to reach a steady state.

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Section: Introductionmentioning

confidence: 99%

Particle heating and acceleration by reconnecting and nonreconnecting current sheets

Sioulas

Isliker

Vlahos

2021

A&A

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“…Multi-islands are produced by tearing instability and accelerate electrons through adiabatic motions to absorb the magnetic energy released by the contraction of the islands. Therefore, the multi-island acceleration timescale is comparable to the MHD MR process, and it is difficult to obtain the fully kinetic electron power-law energy spectra within the desired timescale due to the particle confinement of magnetic islands (Che & Zank 2019). As a comparison, the magnetic vortical MR acceleration process (a stochastic process) can produce the desired power-law energy spectra within about the ion gyrofrequency Ω i , which is a tiny fraction of the whole MR process (Che & Zank 2020;Che et al 2021).…”

Section: Vortical Reconnection Acceleration Modelmentioning

confidence: 99%

“…Extensive studies have been performed on modeling the generation of the inverse electron energy power-law distribution. Some of the kinetic mechanisms, such as multi-island contraction acceleration in MR (Drake et al 2006;Zank et al 2014), are not efficient enough to produce power-law energy spectra in the desired timescale due to their adiabatic invariant acceleration property (Che & Zank 2019). Stochastic kinetic turbulence models can efficiently produce the desired spectra, but it is unclear how to produce the proposed kinetic turbulence in MR, and the kinetic turbulence is usually assumed to be fully developed (Pritchett & Wu 1979;Kliem 1994;Miller et al 1997;Drake et al 2006;Medvedev & Zakutnyaya 2009;Petrosian 2012;Nishizuka & Shibata 2013;Klein & Dalla 2017).…”

Section: Introductionmentioning

confidence: 99%

The Scaling of Vortical Electron Acceleration in Thin-current Magnetic Reconnection and Its Implications in Solar Flares

Crawford,

Che,

Benz

2024

ApJ

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To investigate how magnetic reconnection (MR) accelerates electrons to a power-law energy spectrum in solar flares, we explore the scaling of a kinetic model proposed by Che & Zank (CZ) and compare it to observations. Focusing on thin current sheet MR particle-in-cell (PIC) simulations, we analyze the impact of domain size on the evolution of the electron Kelvin–Helmholtz instability (EKHI). We find that the duration of the growth stage of the EKHI ( t G ∼ Ω e − 1 ) is short and remains nearly unchanged because the electron gyrofrequency Ω e is independent of domain size. The quasi-steady stage of the EKHI (t MR) dominates the electron acceleration process and scales linearly with the size of the simulations as L/v A0, where v A0 is the Alfvén speed. We use the analytical results obtained by CZ to calculate the continuous temporal evolution of the electron energy spectra from PIC simulations and linearly scale them to solar flare observational scales. For the first time, an electron acceleration model predicts the sharp two-stage transition observed in typical soft–hard–harder electron energy spectra, implying that the electron acceleration model must be efficient with an acceleration timescale that is a small fraction of the duration of solar flares. Our results suggest that we can use PIC MR simulations to investigate the observational electron energy spectral evolution of solar flares if the ratio t MR/t G is sufficiently small, i.e., ≲10%.

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“…As a particle accelerator, magnetic reconnection should really be thought of as an acceleration environment, not a single mechanism. The extent to which electrons vs. ions get accelerated and which mechanisms operate in a reconnection region can depend on plasma conditions, boundary conditions, and system size [129,130,131,132]. Mechanisms operating in reconnection environments may include some combination of direct electric field acceleration, stochastic Fermi acceleration from turbulence, first order Fermi acceleration from converging flows or within magnetic blobs, and downstream fast shocks.…”

Section: What Causes Jet Instability and Local Sites Of Particle Acce...mentioning

confidence: 99%

Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?

Blackman,

Lebedev

2020

Preprint

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The physics of astrophysical jets can be divided into three regimes: (i) engine and launch (ii) propagation and collimation, (iii) dissipation and particle acceleration. Since astrophysical jets comprise a huge range of scales and phenomena, practicality dictates that most studies of jets intentionally or inadvertently focus on one of these regimes, and even therein, one body of work may be simply boundary condition for another. We first discuss long standing persistent mysteries that pertain the physics of each of these regimes, independent of the method used to study them. This discussion makes contact with frontiers of plasma astrophysics more generally. While observations theory, and simulations, and have long been the main tools of the trade, what about laboratory experiments? Jet related experiments have offered controlled studies of specific principles, physical processes, and benchmarks for numerical and theoretical calculations. We discuss what has been done to date on these fronts. Although experiments have indeed helped us to understand certain processes, proof of principle concepts, and benchmarked codes, they have yet to solved an astrophysical jet mystery on their own. A challenge is that experimental tools used for jet-related experiments so far, are typically not machines originally designed for that purpose, or designed with specific astrophysical mysteries in mind. This presents an opportunity for a different way of thinking about the development of future platforms: start with the astrophysical mystery and build an experiment to address it.

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A Brief Review on Particle Acceleration in Multi-island Magnetic Reconnection

Cited by 7 publications

References 73 publications

Particle heating and acceleration by reconnecting and nonreconnecting current sheets

Particle heating and acceleration by reconnecting and nonreconnecting current sheets

The Scaling of Vortical Electron Acceleration in Thin-current Magnetic Reconnection and Its Implications in Solar Flares

Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?

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