Tearing-mode stability properties of a diffuse anisotropic field-reversed ion layer at marginal stability

Chen, James

doi:10.1063/1.863336

Cited by 12 publications

(6 citation statements)

References 17 publications

(3 reference statements)

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“…Chen and Davidson [159] have applied a bifurcation of equilibrium analysis to a one-dimensional system, where f 0 has an explicit dependence upon P z (above that contained implicitly in H o ), i.e. to a system anisotropic in r-z.…”

Section: W = I F D 3 Xmentioning

confidence: 99%

Field-reversed configurations with a component of energetic particles

Finn¹,

Sudan²

1982

Nucl. Fusion

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This review is concerned with the physics of field-reversed configurations created by energetic particles of large orbits, of which the earliest example is the Astron. The Astron concept has evolved into the Ion Ring Compressor in which a low-energy ring of ions is magnetically compressed to high energy for heating the confined plasma to thermonuclear ignition. A third version is the hybrid in which field reversal is created both by plasma currents as in a θ-pinch or a spheromak and a component of energetic large orbit ions to provide heating energy as well as improved stability. This paper treats first the injection, trapping, and formation of electron and ion rings from a theoretical standpoint as well as presenting the principal experimental results. The equilibria and the characteristics of the particle orbits are discussed in some detail including conditions under which the orbits cease to be integrable and pass to a stochastic description. The theory of magnetic compression of rings and the classical transport of heat and particles of the plasma confined in the closed-poloidal-field-line region is presented. The bulk of the review is concerned with low-frequency stability of such configurations by means of a generalized energy principle for treating the large-orbit particles in the Vlasov limit. The pathology of all possible unstable modes is discussed at some length. We conclude with an exhaustive survey of microinstabilities driven by the energetic particle current for a special model and conclude that most of them are stabilized by strong gradients in density and magnetic field. A brief discussion on drift modes follows. Our present theoretical understanding of these systems, although still incomplete in some respects, nevertheless leads to the view that the promise of the very favourable features of fusion reactors based on these concepts is a sufficient impetus for their continued experimental and theoretical study.

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Section: W = I F D 3 Xmentioning

confidence: 99%

Field-reversed configurations with a component of energetic particles

Finn¹,

Sudan²

1982

Nucl. Fusion

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Section: Introductionmentioning

confidence: 99%

“…There is a relatively large body of work on the impact of pressure anisotropy on tearing modes (Chen & Davidson 1981;Coppi 1983;Chen & Palmadesso 1984;Chen & Lee 1985;Ambrosiano, Lee & Fu 1986;Shi, Lee & Fu 1987;Karimabadi, Daughton & Quest 2005;Haijima et al 2008;Quest, Karimabadi & Daughton 2010;Matteini et al 2013;Gingell, Burgess & Matteini 2015), as well as on the production and impact of pressure anisotropy during the reconnection process itself (Drake et al 2006;Le et al 2009;Schoeffler, Drake & Swisdak 2011;Egedal, Le & Daughton 2013;Cassak et al 2015;Le et al 2016). Here we focus instead on the pressure anisotropy adiabatically produced during the CS formation, prior to the reconnection event.…”

Section: Introductionmentioning

confidence: 99%

Onset of magnetic reconnection in a collisionless, high- plasma

Alt

Kunz

2019

J. Plasma Phys.

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In a magnetized, collisionless plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase in the magnetic-field strength in such a plasma thus leads to an increase in the thermal pressure perpendicular to the field lines. Above a β-dependent threshold (where β is the ratio of thermal to magnetic pressure), this pressure anisotropy drives the mirror instability, producing strong distortions in the field lines on ion-Larmor scales. The impact of this instability on magnetic reconnection is investigated using a simple analytical model for the formation of a current sheet (CS) and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a CS in a collisionless plasma, coupled with the low threshold for the mirror instability in a high-β plasma, imply that the geometry of reconnecting magnetic fields can differ radically from the standard Harris-sheet profile often used in simulations of collisionless reconnection. As a result, depending on the rate of CS formation and the initial CS thickness, tearing modes whose growth rates and wavenumbers are boosted by this difference may disrupt the mirror-infested CS before standard tearing modes can develop. A quantitative theory is developed to illustrate this process, which may find application in the tearing-mediated disruption of kinetic magnetorotational "channel" modes. †

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“…Some authors (e.g. Chen & Davidson 1981;Coppi 1983;Quest et al 2010) have addressed this problem in the framework of linear theory. In particular Chen & Palmadesso (1984) have predicted that in the presence of a T ⊥ > T proton anisotropy, the growth rate of the tearing instability is expected to increase with respect the isotropic case, and that the most unstable mode is shifted to larger wavenumbers.…”

Section: Introductionmentioning

confidence: 99%

Proton Temperature Anisotropy and Magnetic Reconnection in the Solar Wind: Effects of Kinetic Instabilities on Current Sheet Stability

Matteini

Landi

Velli

et al. 2013

ApJ

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We investigate the role of kinetic instabilities driven by a proton anisotropy on the onset of magnetic reconnection by means of two-dimensional hybrid simulations. The collisionless tearing of a current sheet is studied in the presence of a proton temperature anisotropy in the surrounding plasma. Our results confirm that anisotropic protons within the current sheet region can significantly enhance/stabilize the tearing instability of the current. Moreover, fluctuations associated with linear instabilities excited by large proton temperature anisotropies can significantly influence the stability of the plasma and perturb the current sheets, triggering the tearing instability. We find that such a complex coupling leads to a faster tearing evolution in the T ⊥ > T regime when an ion-cyclotron instability is generated by the anisotropic proton distribution functions. On the contrary, in the presence of the opposite anisotropy, fire-hose fluctuations excited by the unstable background protons with T < T ⊥ are not able to efficiently destabilize current sheets, which remain stable for a long time after fire-hose saturation. We discuss possible influences of this novel coupling on the solar wind and heliospheric plasma dynamics.

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Tearing-mode stability properties of a diffuse anisotropic field-reversed ion layer at marginal stability

Cited by 12 publications

References 17 publications

Field-reversed configurations with a component of energetic particles

Field-reversed configurations with a component of energetic particles

Onset of magnetic reconnection in a collisionless, high- plasma

Proton Temperature Anisotropy and Magnetic Reconnection in the Solar Wind: Effects of Kinetic Instabilities on Current Sheet Stability

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