Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles

Yoshida, Zensho; Saitoh, H.; Morikawa, Junji; Yano, Yoshihisa; Watanabe, Sho; Ogawa, Yuichi

doi:10.1103/physrevlett.104.235004

Cited by 67 publications

(82 citation statements)

References 28 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 self-organization of a magnetospheric plasma confinement, both in astronomical magnetic dipoles 2,3 and laboratory ones [4][5][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.…”

mentioning

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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“…The RT-1 device, shown in Fig. 46 has recently demonstrated good confinement for single-component electron plasmas Yoshida et al, 2010). Specifically, an electron plasma of density 10 11 m −3 was confined for 300 s. This device could be filled with positrons from an MCT using the methods described above for the APEX stellarator.…”

Section: Classical Electron-positron (Pair) Plasmasmentioning

confidence: 99%

Plasma and trap-based techniques for science with positrons

Danielson¹,

Dubin²,

Greaves³

et al. 2015

Rev. Mod. Phys.

215

217

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In recent years, there has been a wealth of new science involving low-energy antimatter (i.e., positrons and antiprotons) at energies ranging from 10 2 to less than 10 −3 eV. Much of this progress has been driven by the development of new plasma-based techniques to accumulate, manipulate and deliver antiparticles for specific applications. This article focuses on the advances made in this area using positrons. However many of the resulting techniques are relevant to antiprotons as well. An overview is presented of relevant theory of single-component plasmas in electromagnetic traps. Methods are described to produce intense sources of positrons and to efficiently slow the typically energetic particles thus produced. Techniques are described to trap positrons efficiently and to cool and compress the resulting positron gases and plasmas. Finally, the procedures developed to deliver tailored pulses and beams (e.g., in intense, short bursts, or as quasi-monoenergetic continuous beams) for specific applications are reviewed. The status of development in specific application areas is also reviewed. One example is the formation of antihydrogen atoms for fundamental physics [e.g., tests of invariance under charge conjugation, parity inversion and time reversal (the CPT theorem), and studies of the interaction of gravity with antimatter]. Other applications discussed include atomic and materials physics studies and study of the electron-positron many-body system, including both classical electron-positron plasmas and the complementary quantum system in the form of Bose-condensed gases of positronium atoms. Areas of future promise are also discussed. The review concludes with a brief summary and a list of outstanding challenges.

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“…It is characterized by high-β stability and excellent confinement properties [3]. Stable confinement of high-β plasmas has been demonstrated in dipole magnetic fields generated by levitated superconducting magnets in the Ring Trap 1 (RT-1) [4], the Mini Ring Trap (Mini-RT) [5], and the Levitated Dipole Experiment (LDX) [6,7]. In the first series of experiments in RT-1 [8][9][10][11], a plasma has been generated by using an electron cyclotron resonance heating (ECH) with 8.2 and 2.45 GHz microwaves [11,12].…”

Section: Introductionmentioning

confidence: 99%

Observation of a new high-β and high-density state of a magnetospheric plasma in RT-1

et al. 2014

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A new high-β and high-density state is reported for a plasma confined in a laboratory magnetosphere. In order to expand the parameter regime of an electron cyclotron resonance heating (ECH) experiment, the 8.2 GHz microwave power of the Ring Trap 1 (RT-1) device has been upgraded with the installation of a new waveguide system. The rated input power launched from a klystron was increased from 25 to 50 kW, which enabled the more stable formation of a hot-electron high-β plasma. The diamagnetic signal (the averaged value of four magnetic loops signals) of a plasma reached 5.2 mWb. According to a two-dimensional Grad-Shafranov analysis, the corresponding local β value is close to 100 %.

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Magnetospheric Vortex Formation: Self-Organized Confinement of Charged Particles

Cited by 67 publications

References 28 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

Plasma and trap-based techniques for science with positrons

Observation of a new high-β and high-density state of a magnetospheric plasma in RT-1

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