Observation of particle acceleration in laboratory magnetosphere

Kawazura, Yohei; Yoshida, Zensho; Nishiura, M.; Saitoh, H.; Yano, Yoshihisa; Nogami, T.; Sato, Naoki; Yamasaki, M.; Kashyap, A.; Mushiake, T.

doi:10.1063/1.4935894

Cited by 18 publications

(22 citation statements)

References 29 publications

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“…Such structurization and anisotropic heating are also consistent with the laboratory experiment results [4][5][6]14 . This work was supported by JSPS KAKENHI Grant No.…”

supporting

confidence: 79%

“…The Van Allen radiation belt is believed to be the product of such process [8][9][10] (electrons in an ultra-relativistic regime are created by non-local acceleration mechanisms, such as wave particle interaction [11][12][13] ). Recently, the inward diffusion heating was observed in laboratory magnetosphere experiments 14,15 . As mentioned above, magnetic field does not produce a potential energy (unlike gravity or electrostatic force); hence the concentration and acceleration are not due to centripetal force.…”

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confidence: 99%

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Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

et al. 2016

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Charged particles in a magnetosphere are spontaneously attracted to a planet while increasing their kinetic energy via inward diffusion process. A constraint on particles' micro-scale adiabatic invariants restricts the class of motions available to the system, giving rise to a proper frame on which particle diffusion occurs. We investigate the inward diffusion process by numerical simulation of particles on constrained phase space. The results reveal the emergence of inhomogeneous density gradient and anisotropic heating, which is consistent with spacecraft observations, experimental observations, and the recently formulated diffusion model on the constrained phase space.Magnetospheres are the prototypical systems that demonstrate spontaneous confinement of plasmas by magnetic force. Since magnetic force is free of mechanical work, its effect does not appear as an energy term in the Boltzmann distribution (which is in marked contrast with the gravitational confinement created by a star). Instead, the magnetic field manifests itself as topological constraints in the dynamics and equilibrium structures; for example, see Ref. 1 for a recent formulation of magnetic confinement in the perspective of phasespace foliation.The self-organization of a magnetospheric plasma confinement, both in astronomical magnetic dipoles 2,3 and laboratory ones 4-6 , requires a spontaneous mechanism that 'creates' density gradients. As a concomitant effect, particles are accelerated (heated) as they climb up the density gradients 7 ; conservation of first and second adiabatic invariants along the inward displacement increases particle's kinetic energy. The Van Allen radiation belt is believed to be the product of such process [8][9][10] (electrons in an ultra-relativistic regime are created by non-local acceleration mechanisms, such as wave particle interaction [11][12][13] ). Recently, the inward diffusion heating was observed in laboratory magnetosphere experiments 14,15 . As mentioned above, magnetic field does not produce a potential energy (unlike gravity or electrostatic force); hence the concentration and acceleration are not due to centripetal force. The driving force for such 'up-hill diffusion' 16 and acceleration may come from some fluctuations. The key element of the mechanism is, then, the symmetry breaking that selects the preferential direction for particles to penetrate. The symmetry breaking appears in the metric of the phase space; the root cause of an inhomogeneous metric is the topological constraint imposed on magnetized particles by the adiabatic invariants such as magnetic moments 1,17,18 .The early theoretical studies developed an empirical Fokker-Planck type diffusion model on a phase space spanned by adiabatic invariants 19 and explained planetary radiation belt with inhomogeneous density gradients (see Ref. 20 and references therein). This theory was later developed into a unified model according to which the number of particles contained in each magnetic flux tube tends to be homogenized, with the result tha...

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“…Such structurization and anisotropic heating are also consistent with the laboratory experiment results [4][5][6]14 . This work was supported by JSPS KAKENHI Grant No.…”

supporting

confidence: 79%

mentioning

confidence: 99%

Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

et al. 2016

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“…Both the ECR and ICR plasma heating methods can produce high-energy electrons and ions, respectively, which imply anisotropic temperatures of the resonant particles, with transverse temperature T ⊥ (relative to the confining magnetic field) greater than the parallel temperature T || . These anisotropies are observed in RT-1 studying the particle acceleration in LDM plasma [7].…”

Section: Introductionmentioning

confidence: 93%

“…The dipole confinement concept to simulate a magnetosphere in laboratory conditions was originally proposed by Hasegawa [1]. Presently, there are active experiments on the plasma creation, confinement and heating in devices such as Levitated Dipole eXperiment (LDX) [2,3] and Ring Trap 1 (RT-1) [4][5][6][7]. The RT-1 device is a laboratory dipole magnetosphere (LDM) created by a levitated superconducting ring magnet.…”

Section: Introductionmentioning

confidence: 99%

Cyclotron Electromagnetic Instabilities in a Laboratory Dipole Magnetospheric Plasma with bi-Kappa Distributions

Grishanov

Azarenkov

Lazar

2017

Plasma and Fusion Research

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The transverse dielectric susceptibility elements are derived for electromagnetic cyclotron waves in an axisymmetric laboratory dipole magnetosphere accounting for the cyclotron and bounce resonances of trapped and untrapped particles. A bi-Kappa (or bi-Lorentzian) distribution function is invoked to model the energetic particles with anisotropic temperature. The steady-state two-dimensional (2D) magnetic field is modeled by laboratory dipole approximation for a superconducting ring current of finite radius. Derived for field-aligned circularlypolarized waves the dispersion relations are suitable for analyzing both the whistler instability in the range below the electron-cyclotron frequency, and the proton-cyclotron instability in the range below the ion-cyclotron frequency. The instability growth rates in the 2D laboratory magnetosphere are defined by the contributions of energetic particles to the imaginary part of transverse susceptibility.

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“…A diversity of plasmas is expected to be realized with RT-1. Some of these plasmas such as inward diffusion and selforganized plasmas have been observed [2][3][4][5][6][7]. A dipole magnetic field stably and naturally confines plasma in a high beta state like magnetosphere plasma of planets.…”

Section: Introductionmentioning

confidence: 99%

Increase in Ion Temperature by Slow Wave Heating in Magnetosphere Plasma Device RT-1

Nishiura

Yoshida

Yano

et al. 2016

Plasma and Fusion Research

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Ion cyclotron range of frequencies (ICRF) heating with a frequency of a few MHz and an input power of 10 kW was applied for the first time, to the best of our knowledge, in a magnetosphere plasma device. An antenna was installed near the pole of a dipole field for slow-wave excitation. Further, a ∩-shaped antenna was implemented and characterized for efficient ion heating. Electron cyclotron heating with an input power of 8 kW sustained helium plasmas with a fill gas pressure of 3 mPa. ICRF heating was then superimposed onto the target plasma (H, D, and He). While the ICRF power was turned on, the increase in ion temperatures was observed for low-pressure helium plasmas. However, the temperature increase was not clearly observed for hydrogen and deuterium plasmas. We discuss the experimental results in terms of power absorption based on result calculated with the TASK/WF2 code.

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Observation of particle acceleration in laboratory magnetosphere

Cited by 18 publications

References 29 publications

Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

Cyclotron Electromagnetic Instabilities in a Laboratory Dipole Magnetospheric Plasma with bi-Kappa Distributions

Increase in Ion Temperature by Slow Wave Heating in Magnetosphere Plasma Device RT-1

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