Helicons in Unbounded Plasmas

Stenzel, R. L.; Urrutia, J. M.

doi:10.1103/physrevlett.114.205005

Cited by 38 publications

(19 citation statements)

References 14 publications

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“…We can regard the initial field line as the background field, and the final field line as the background field plus the perturbations to this field. If the initial field line is stretched so that it mimics a uniform background field (as in the bottom subfigure), we can see that the spatial helicity of the final field corresponds 43 to the conversion region (red rectangle) acting as the source of two whistler waves propagating away from this source in the 6y directions. This picture is consistent with recent spacecraft observations 35,37,38 where the conversion region was a possible source for whistler waves towards the outflow regions.…”

Section: Whistler Wave Generationmentioning

confidence: 99%

An intuitive two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation

Yoon

Bellan

2018

Physics of Plasmas

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An intuitive and physical two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation is presented in the framework of 3D electron-magnetohydrodynamics. In this regime, canonical circulation ðQ ¼ m e r Â u þ q e BÞ flux tubes can be defined in analogy to magnetic flux tubes in ideal magnetohydrodynamics. Following the 3D behavior of these Q flux tubes provides a new perspective on collisionless reconnection-a perspective that has been hard to perceive via examinations of 2D projections. This shows that even in a 2D geometry with an ignorable coordinate, a 3D examination is essential for a full comprehension of the process. Intuitive answers are given to three main questions in collisionless reconnection: why is reconnection spontaneous, why do particles accelerate extremely fast, and why are whistler waves generated? Possible extensions to other regimes are discussed.

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Section: Whistler Wave Generationmentioning

confidence: 99%

An intuitive two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation

Yoon

Bellan

2018

Physics of Plasmas

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“…Stenzel and Urrutia 35 recently reported laboratory experiments where whistler waves were excited by small loop antennas in unbounded plasmas in a uniform background magnetic field. The numerical code was arranged to model the morphology of the antenna currents in the experiment, and the experimental wave propagation observations were successfully replicated.…”

Section: Dispersion Relation and Whistler Wave Testmentioning

confidence: 99%

A generalized two-fluid picture of non-driven collisionless reconnection and its relation to whistler waves

Yoon

Bellan

2017

Physics of Plasmas

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A generalized, intuitive two-fluid picture of 2D non-driven collisionless magnetic reconnection is described using results from a full-3D numerical simulation. The relevant two-fluid equations simplify to the condition that the flux associated with canonical circulation Q ¼ m e r Â u e þ q e B is perfectly frozen into the electron fluid. In the reconnection geometry, flux tubes defined by Q are convected with the central electron current, effectively stretching the tubes and increasing the magnitude of Q exponentially. This, coupled with the fact that Q is a sum of two quantities, explains how the magnetic fields in the reconnection region reconnect and give rise to strong electron acceleration. The Q motion provides an interpretation for other phenomena as well, such as spiked central electron current filaments. The simulated reconnection rate was found to agree with a previous analytical calculation having the same geometry. Energy analysis shows that the magnetic energy is converted and propagated mainly in the form of the Poynting flux, and helicity analysis shows that the canonical helicity Ð P Á Q dV as a whole must be considered when analyzing reconnection. A mechanism for whistler wave generation and propagation is also described, with comparisons to recent spacecraft observations. Published by AIP Publishing. [http://dx.

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“…Such 'helicoid' waves carry linear field momentum and angular field momentum which can be transferred to particles on atomic scales. Helicon waves in plasmas can have the same properties but have just begun to realize its potential usefulness [17]. Thus similar phenomena can exist in different fields of physics ranging from the atomic scale to the astrophysical scale and the purpose of this paper is to point out the common connections.…”

Section: Brief Historical Backgroundmentioning

confidence: 96%

“…The latter exerts a torque on particles or waves which alter the field rotation. Since whistler modes with helical phase surfaces exist in both bounded and unbounded plasmas, a more general definition of helicons should be whistler modes with orbital angular momentum [17]. The angular momentum has two contributions, one from the circular polarization of whistlers and another one from the azimuthal wave propagation, referred to as orbital angular momentum.…”

Section: Heliconsmentioning

confidence: 99%

Whistler waves with angular momentum in space and laboratory plasmas and their counterparts in free space

Stenzel

2016

Advances in Physics: X

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Electromagnetic waves with helical phase surfaces arise in different fields of physics such as space plasmas, laboratory plasmas, solid-state physics, atomic, molecular and optical sciences. Their common features are the wave orbital angular momentum associated with the circular wave propagation around the axis of wave propagation. In plasmas these waves are called helicons. When particles or waves change the field momentum they experience a pressure and a torque which can lead to useful applications. In plasmas electrons can damp or excite rotating whistlers, depending on the electron distribution function in velocity space. A magnetized plasma is an anisotropic medium in which electromagnetic waves propagate differently than in space. Phase and group velocities are different such that wave focusing and wave reflections are different from those in free space. Electrons experience Doppler shifts and cyclotron resonance which creates wave damping and growth. All media exhibit nonlinear effects which do not occur in free space. Common and different features of vortex waves in different fields will be reviewed. However, a comprehensive review of this vast field is not possible and further readings are referred to the cited literature. ARTICLE HISTORY

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Helicons in Unbounded Plasmas

Cited by 38 publications

References 14 publications

An intuitive two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation

An intuitive two-fluid picture of spontaneous 2D collisionless magnetic reconnection and whistler wave generation

A generalized two-fluid picture of non-driven collisionless reconnection and its relation to whistler waves

Whistler waves with angular momentum in space and laboratory plasmas and their counterparts in free space

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