Helical Magnetic Cavities: Kinetic Model and Comparison with MMS Observations

<p>Magnetic cavities are sudden depressions of magnetic field strength widely observed in the space plasma environments, which are often accompanied by plasma density and pressure enhancement. To describe these cavities, a self-consistent kinetic model has been proposed as an equilibrium solution to the Vlasov-Maxwell equations. However, observations from the Magnetospheric Multi-Scale (MMS) constellation have shown the existence of helical magnetic cavities characterized by the presence of azimuthal magnetic field, which could not be reconstructed by the aforementioned model. Here, we take into account another invariant of motion, the canonical axial momentum, to construct the particle distributions and accordingly modify the equilibrium model. The reconstructed magnetic cavity shows excellent agreement with the MMS1 observations not only in the electromagnetic field and plasma moment profiles but also in electron pitch-angle distributions. With the same set of parameters, the model also predicts signatures of the neighboring MMS3 spacecraft, matching its observations satisfactorily.</p>

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Unmagnetized diffusion for azimuthally symmetric wave and particle distributions

Journal of Plasma Physics ◽

10.1017/s0022377800013192 ◽

1988 ◽

Vol 40 (1) ◽

pp. 179-198 ◽

Cited By ~ 5

Author(s):

P. B. Dusenbery ◽

L. R. Lyons

Keyword(s):

Magnetic Field ◽

Diffusion Coefficients ◽

Pitch Angle ◽

Particle Distribution ◽

Ion Beam ◽

Distribution Model ◽

Sound Waves ◽

Linear Diffusion ◽

Particle Distributions ◽

Diffusion Rates

The general equations describing the quasi-linear diffusion of charged particles from resonant interactions with a spectrum of electrostatic waves are given, assuming the wave and particle distributions to be azimuthally symmetric. These equations apply when a magnetic field organizes the wave and particle distributions in space, but when the local interaction between the waves and particles can be evaluated assuming that no magnetic field is present. Such diffusion is, in general, two-dimensional and is similar to magnetized diffusion. The connection between the two types of diffusion is presented. In order to apply the general quasi-linear diffusion coefficients in pitch angle and speed, a specific particle-distribution model is assumed. An expression for the unmagnetized dielectric function is derived and evaluated for the assumed particle distribution model. It is found that slow-mode ion-sound waves are unstable for the range of plasma parameters considered. A qualitative interpretation of unmagnetized diffusion is presented. The diffusion coefficients are then evaluated for resonant ion interactions with ion-sound waves. The results illustrate how resonant ion diffusion rates vary with pitch angle and speed, and how the diffusion rates depend upon the distribution of wave energy in k–space. The results of this study have relevance for ion beam heating in the plasma-sheet boundary layer and upstream of the earth's bow shock.

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Collisional alpha transport in a weakly rippled magnetic field

Journal of Plasma Physics ◽

10.1017/s0022377819000151 ◽

2019 ◽

Vol 85 (2) ◽

Cited By ~ 1

Author(s):

Peter J. Catto

Keyword(s):

Magnetic Field ◽

Boundary Layer ◽

Pitch Angle ◽

High Field ◽

Fusion Reactor ◽

Alpha Particles ◽

Boundary Layer Problem ◽

Self Consistent ◽

Consistent Manner ◽

Layer Problem

To properly treat the collisional transport of alpha particles due to a weakly rippled tokamak magnetic field the tangential magnetic drift due to its gradient (the $\unicode[STIX]{x1D735}B$ drift) and pitch angle scatter must be retained. Their combination gives rise to a narrow boundary layer in which collisions are able to match the finite trapped response to the ripple to the vanishing passing response of the alphas. Away from this boundary layer collisions are ineffective. There the $\unicode[STIX]{x1D735}B$ drift of the alphas balances the small radial drift of the trapped alphas caused by the ripple. A narrow collisional boundary layer is necessary since this balance does not allow the perturbed trapped alpha distribution function to vanish at the trapped–passing boundary. The solution of this boundary layer problem allows the alpha transport fluxes to be evaluated in a self-consistent manner to obtain meaningful constraints on the ripple allowable in a tokamak fusion reactor. A key result of the analysis is that collisional alpha losses are insensitive to the ripple near the equatorial plane on the outboard side where the ripple is high. As the high field side ripple is normally very small, collisional $\sqrt{\unicode[STIX]{x1D708}}$ ripple transport is unlikely to be a serious issue.

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Multi-scale magnetic field intermittence in the plasma sheet

Annales Geophysicae ◽

10.5194/angeo-21-1955-2003 ◽

2003 ◽

Vol 21 (9) ◽

pp. 1955-1964 ◽

Cited By ~ 40

Author(s):

Z. Vörös ◽

W. Baumjohann ◽

R. Nakamura ◽

A. Runov ◽

T. L. Zhang ◽

...

Keyword(s):

Magnetic Field ◽

Plasma Sheet ◽

Large Scale ◽

Sliding Window ◽

Space Plasma ◽

Space Plasma Physics ◽

Multi Scale ◽

Bursty Bulk Flow ◽

Field Fluctuations ◽

Scale Motion

Abstract. This paper demonstrates that intermittent magnetic field fluctuations in the plasma sheet exhibit transitory, localized, and multi-scale features. We propose a multifractal-based algorithm, which quantifies intermittence on the basis of the statistical distribution of the "strength of burstiness", estimated within a sliding window. Interesting multi-scale phenomena observed by the Cluster spacecraft include large-scale motion of the current sheet and bursty bulk flow associated turbulence, interpreted as a cross-scale coupling (CSC) process.Key words. Magnetospheric physics (magnetotail; plasma sheet) – Space plasma physics (turbulence)

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Self-consistent kinetic model of nested electron- and ion-scale magnetic cavities in space plasmas

Nature Communications ◽

10.1038/s41467-020-19442-0 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Jing-Huan Li ◽

Fan Yang ◽

Xu-Zhi Zhou ◽

Qiu-Gang Zong ◽

Anton V. Artemyev ◽

...

Keyword(s):

Kinetic Model ◽

Energy Partition ◽

Multi Scale ◽

Self Organized ◽

Laboratory Plasmas ◽

Self Consistent ◽

Scale Structures ◽

Kinetics Of ◽

Theoretical Insight ◽

Insight Into

Abstract NASA’s Magnetospheric Multi-Scale (MMS) mission is designed to explore the proton- and electron-gyroscale kinetics of plasma turbulence where the bulk of particle acceleration and heating takes place. Understanding the nature of cross-scale structures ubiquitous as magnetic cavities is important to assess the energy partition, cascade and conversion in the plasma universe. Here, we present theoretical insight into magnetic cavities by deriving a self-consistent, kinetic theory of these coherent structures. By taking advantage of the multipoint measurements from the MMS constellation, we demonstrate that our kinetic model can utilize magnetic cavity observations by one MMS spacecraft to predict measurements from a second/third spacecraft. The methodology of “observe and predict” validates the theory we have derived, and confirms that nested magnetic cavities are self-organized plasma structures supported by trapped proton and electron populations in analogous to the classical theta-pinches in laboratory plasmas.

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SELF-CONSISTENT DISTRIBUTIONS FOR CHARGED PARTICLE BEAM IN MAGNETIC FIELD

International Journal of Modern Physics A ◽

10.1142/s0217751x09044322 ◽

2009 ◽

Vol 24 (05) ◽

pp. 816-842 ◽

Cited By ~ 8

Author(s):

OLEG I. DRIVOTIN ◽

DMITRI A. OVSYANNIKOV

Keyword(s):

Magnetic Field ◽

Charged Particle ◽

Particle Density ◽

Axial Direction ◽

Particle Beam ◽

Integrals Of Motion ◽

Charged Particle Beam ◽

Particle Distributions ◽

Dimensional Phase Space ◽

Self Consistent

The problem of constructing self-consistent stationary particle distributions in four-dimensional phase space is considered for an azimuthally symmetric charged particle beam in a longitudinal magnetic field. In the general case of a longitudinally nonuniform beam, it is assumed that the magnetic field and the radius of the beam cross-section can slowly vary in the axial direction. The simplest case of a longitudinally uniform beam is studied in more detail. The approach applied here is to analyze the particle density in the space of integrals of motion. The relations between this density, the phase density, and the density in the configuration space are obtained. The set of admissible values of integrals of motion for a radially confined beam is examined. The construction of new self-consistent distributions consists in the specifying of some function defined on this set. Wide classes of new distributions are found. In particular cases, some of these distributions are identical to those known before, for example, the Kapchinsky-Vladimirsky distribution.

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