Anisotropy in Broad Component of H&lt;i&gt;α&lt;/i&gt; Line in the Magnetospheric Device RT-1&lt;sup&gt; &lt;/sup&gt;

Kawazura, Yohei; Takahashi, N.; Yoshida, Zensho; Nishiura, M.; Nogami, T.; Kashyap, A.; Yano, Yoshihisa; Saitoh, H.; Yamasaki, M.; Mushiake, T.; Nakatsuka, Masaya

doi:10.1585/pfr.11.2402024

Plasma and Fusion Research

2016

DOI: 10.1585/pfr.11.2402024

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Anisotropy in Broad Component of H<i>α</i> Line in the Magnetospheric Device RT-1<sup> </sup>

Yohei Kawazura

N. Takahashi

Zensho Yoshida

et al.

Abstract: Temperature anisotropy in broad component of Hα line was found in the ring trap 1 (RT-1) device by Doppler spectroscopy. Since hot hydrogen neutrals emitting a broad component are mainly produced by charge exchange between neutrals and protons, the anisotropy in the broad component is the evidence of proton temperature anisotropy generated by betatron acceleration.

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

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Temperature anisotropy governed electrical conductivity tensor in a steady state dipole plasma: Spatially resolved experiments and modeling

Nanda

Bhattacharjee

2022

Physics of Plasmas

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A generalization of electrical conductivity in a plasma confined in a dipole magnetic field, in the presence of temperature anisotropy is presented. The anisotropy governed by the magnetic field distribution is found to be significant in the strong field region, and has a considerable effect on Pedersen and longitudinal conductivity of electrons over Hall conductivity, whereas the effect of temperature anisotropy on Hall conductivity can be observed in the case of ions. The work reveals new features in the conductivity tensor arising due to the temperature anisotropy and bidirectional nature of the dipole field, by incorporating all possible particle drifts, which would be helpful to enhance the understanding of electrical conduction in both laboratory and space dipole plasmas.

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Anisotropy in Broad Component of H<i>α</i> Line in the Magnetospheric Device RT-1<sup> </sup>

Cited by 2 publications

References 22 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

Temperature anisotropy governed electrical conductivity tensor in a steady state dipole plasma: Spatially resolved experiments and modeling

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