Impact of the Eulerian chaos of magnetic field lines in magnetic reconnection

Firpo, Marie-Christine; Ettoumi, Wahb; Lifschitz, Agustín; Farengo, Ricardo; Ferrari, Hugo; García-Martínez, Pablo

doi:10.1063/1.4972544

Cited by 5 publications

(3 citation statements)

References 26 publications

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“…As spontaneous magnetic reconnection may start from an instability, such a stage of low-dimensional chaos should precede turbulence and its impact on reconnection in the astrophysical context remains to be explored. A preliminary analysis indicates that, all other things being equal, chaotic magnetic field lines induce an increased rate of energy transfer compared with integrable (laminar) B lines [7].…”

Section: Conclusion and Future Prospectsmentioning

confidence: 98%

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Evidence and relevance of spatially chaotic magnetic field lines in MCF devices

Firpo

Lifschitz

Ettoumi

et al. 2017

Plasma Phys. Control. Fusion

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Numerical evidence for the existence of spatially chaotic magnetic field lines about the collapse phase of tokamak sawteeth with incomplete reconnection is presented. This uses the results of extensive test particle simulations in different sets of electromagnetic perturbations tested against experimental JET measurements. In tokamak sawteeth, that form a laboratory prototype of magnetic reconnection, the relative magnetic perturbation dB B may reach a few percents. This does not apply to tokamak operating regimes dominated by turbulence where dB B is usually not larger than-10 4. However, this small magnetic perturbation being sustained by a large spectrum of modes is shown to be sufficient to ensure the existence of stochastic magnetic field lines. This has important consequences for magnetic confinement fusion where electrons are dominantly governed by the magnetic force. Indeed some overlap between magnetic resonances can locally induce chaotic magnetic field lines enabling the spatial redistribution of the electron population and of its thermal content. As they are the swiftest plasma particles, electrons feed back the most rapid perturbations of the magnetic field.

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Section: Conclusion and Future Prospectsmentioning

confidence: 98%

“…The adverb spatially serves to remind that one refers here to the chaos of magnetic field lines at given times. One could also equivalently talk of Eulerian chaos [7]. We shall now address the questions of the existence and importance of spatially chaotic magnetic field lines in tokamak plasmas.…”

Section: Introductionmentioning

confidence: 99%

Evidence and relevance of spatially chaotic magnetic field lines in MCF devices

Firpo

Lifschitz

Ettoumi

et al. 2017

Plasma Phys. Control. Fusion

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“…The mode is assumed to grow from zero to its saturated value in a time much shorter than the sawtooth period and the exact value of the growth rate is irrelevant for the final result. The effect of the mode is introduced employing a formalism developed to study the dynamics of fast ions and Ni impurities in sawteeth [12][13][14][15][16] while elastic collisions are included using the collision operator described in [17], modified to account for plasma rotation. We find that when the W ions rotate with a frequency which is similar to the rotation frequency of the mode they are expelled from the magnetic axis.…”

Section: Introductionmentioning

confidence: 99%

The effect of a saturated kink on the dynamics of tungsten impurities in the plasma core

Ferrari

Farengo

Clauser

2019

Plasma Phys. Control. Fusion

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We studied the effect of saturated kink-like instabilities on the redistribution of W impurities. A numerical code that follows the exact trajectories of the impurity ions in the total fields and includes collisions was employed. The code is written in CUDA C and runs in graphical processing units, allowing simulations with a large number of particles with modest resources. The total electric and magnetic fields are calculated as the sum of a simple analytical equilibrium (large aspect ratio, circular cross section) plus the fields of the kink mode. Our simulations show that when the W ions have a thermal velocity distribution, with zero mean velocity, the kink has no effect on the W density. However, when we include the plasma rotation and the drag on the impurities, the kink can affect the W density. When the average passing frequency of the W ions is similar to the frequency of the kink mode, the expulsion of W ions from the plasma core is maximized and the W density profile shows a hollow structure. This could have implications for the mitigation of W accumulation.

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Magnetic reconnection: MHD theory and modelling

Pontin

Priest

2022

Living Rev Sol Phys

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In this review we focus on the fundamental theory of magnetohydrodynamic reconnection, together with applications to understanding a wide range of dynamic processes in the solar corona, such as flares, jets, coronal mass ejections, the solar wind and coronal heating. We summarise only briefly the related topics of collisionless reconnection, non-thermal particle acceleration, and reconnection in systems other than the corona. We introduce several preliminary topics that are necessary before the subtleties of reconnection can be fully described: these include null points (Sects. 2.1–2.2), other topological and geometrical features such as separatrices, separators and quasi-separatrix layers (Sects. 2.3, 2.6), the conservation of magnetic flux and field lines (Sect. 3), and magnetic helicity (Sect. 4.6). Formation of current sheets in two- and three-dimensional fields is reviewed in Sect. 5. These set the scene for a discussion of the definition and properties of reconnection in three dimensions that covers the conditions for reconnection, the failure of the concept of a flux velocity, the nature of diffusion, and the differences between two-dimensional and three-dimensional reconnection (Sect. 4). Classical 2D models are briefly presented, including magnetic annihilation (Sect. 6), slow and fast regimes of steady reconnection (Sect. 7), and non-steady reconnection such as the tearing mode (Sect. 8). Then three routes to fast reconnection in a collisional or collisionless medium are described (Sect. 9). The remainder of the review is dedicated to our current understanding of how magnetic reconnection operates in three dimensions and in complex magnetic fields such as that of the Sun’s corona. In Sects. 10–12, 14.1 the different regimes of reconnection that are possible in three dimensions are summarised, including at a null point, separator, quasi-separator or a braid. The role of 3D reconnection in solar flares (Sect. 13) is reviewed, as well as in coronal heating (Sect. 14), and the release of the solar wind (Sect. 15.2). Extensions including the role of reconnection in the magnetosphere (Sect. 15.3), the link between reconnection and turbulence (Sect. 16), and the role of reconnection in particle acceleration (Sect. 17) are briefly mentioned.

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Impact of the Eulerian chaos of magnetic field lines in magnetic reconnection

Cited by 5 publications

References 26 publications

Evidence and relevance of spatially chaotic magnetic field lines in MCF devices

Evidence and relevance of spatially chaotic magnetic field lines in MCF devices

The effect of a saturated kink on the dynamics of tungsten impurities in the plasma core

Magnetic reconnection: MHD theory and modelling

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