Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

Mottez, Fabrice; Génot, Vincent

doi:10.1029/2010ja016367

Cited by 25 publications

(23 citation statements)

References 37 publications

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“…We can see high frequency oscillations that do not propagate; they are simply a noise background oscillating around the plasma frequency (ω = 1). As in Mottez and Génot (2011), this noise is enhanced at the initial position of the wave packets because of an imperfect initialization of the Alfvén wave modes. More interesting, we can see that around time 200, when the two wave packets strongly interact, there is the emergence of an electric structure that does not propagate and that lasts as long as the two wave packets cross each other.…”

Section: F Mottez: Parallel Electric Fieldsmentioning

confidence: 87%

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Non-propagating electric and density structures formed through non-linear interaction of Alfvén waves

Mottez

2012

Ann. Geophys.

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Abstract. In the auroral zone of the Earth, the electron acceleration by Alfvén waves is sometimes seen as a precursor of the non-propagating acceleration structures. In order to investigate how Alfvén waves could generate non-propagating electric fields, a series of simulations of counter-propagating waves in a homogeneous medium is presented. The waves propagate along the ambient magnetic field direction. It is shown that non-propagating electric fields are generated at the locus of the Alfvén waves crossing. These electric fields have a component orientated along the direction of the ambient magnetic field, and they generate a significant perturbation of the plasma density. The non-linear interaction of down and up-going Alfvén waves might be a cause of plasma density fluctuations (with gradients along the magnetic field) on a scale comparable to those of the Alfvén wavelengths. The present paper is mainly focused on the creation process of the non-propagating parallel electric field.

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Section: F Mottez: Parallel Electric Fieldsmentioning

confidence: 87%

“…This way of initializing Alfvén wave packets has already been applied and tested by Mottez and Génot (2011). It was shown that for a single wave packet propagating on a uniform plasma, the packet is not destroyed by the dispersion.…”

Section: F Mottez: Parallel Electric Fieldsmentioning

confidence: 99%

Non-propagating electric and density structures formed through non-linear interaction of Alfvén waves

Mottez

2012

Ann. Geophys.

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“…Thus, the accelerated population represents some beams in energy space. The relaxation of this kind of beam in inhomogeneous plasma results in the generation of low-frequency electrostatic waves (Mottez & Génot 2011). As a result, electron acceleration by KAWs may increase a level of electrostatic turbulence, which effectively scatters electrons.…”

Section: Discussionmentioning

confidence: 99%

Electron trapping and acceleration by kinetic Alfvén waves in solar flares

Artemyev

Zimovets

Rankin

2016

A&A

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Context. Theoretical models and spacecraft observations of solar flares highlight the role of wave-particle interaction for non-local electron acceleration. In one scenario, the acceleration of a large electron population up to high energies is due to the transport of electromagnetic energy from the loop-top region down to the footpoints, which is then followed by the energy being released in dense plasma in the lower atmosphere. Aims. We consider one particular mechanism of non-linear electron acceleration by kinetic Alfvén waves. Here, waves are generated by plasma flows in the energy release region near the loop top. We estimate the efficiency of this mechanism and the energies of accelerated electrons. Methods. We use analytical estimates and test-particle modelling to investigate the effects of electron trapping and acceleration by kinetic Alfvén waves in the inhomogeneous plasma of the solar corona. Results. We demonstrate that, for realistic wave amplitudes, electrons can be accelerated up to 10−1000 keV during their propagation along magnetic field lines. Here the electric field that is parallel to the direction of the background magnetic field is about 10 to 10 3 times the amplitude of the Dreicer electric field. The acceleration mechanism strongly depends on electron scattering which is due to collisions that only take place near the loop footpoints. Conclusions. The non-linear wave-particle interaction can play an important role in the generation of relativistic electrons within flare loops. Electron trapping and coherent acceleration by kinetic Alfvén waves represent the energy cascade from large-scale plasma flows that originate at the loop-top region down to the electron scale. The non-diffusive character of the non-linear electron acceleration may be responsible for the fast generation of high-energy particles.

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“…Mottez and Génot [8] studies the interaction of an isolated Alfven wave packet with a plasma density cavity. Tsiklauri [7] considered particle acceleration by DAWs in the transversely inhomogeneous plasma via full kinetic simulation particularly focusing on the effect of polarization of the waves and different regimes (inertial and kinetic).…”

Section: Introductionmentioning

confidence: 99%

“…As described in Tsiklauri [7,12], presence and damping of magnetohydrodynamic (MHD) waves is of importance to several problems: (i) The solar coronal heating problem [13], (ii) Earth magnetosphere energization in the context of electron acceleration by Alfven harmonic waves and pulses propagating in an auroral plasma cavities [8,[14][15][16]. (iii) Fast acceleration of inner magnetospheric hydrogen and oxygen ions by shock induced ULF waves [17].…”

Section: Introductionmentioning

confidence: 99%

Collisionless, phase-mixed, dispersive, Gaussian Alfven pulse in transversely inhomogeneous plasma

Tsiklauri

2016

Physics of Plasmas

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In the previous works harmonic, phase-mixed, Alfven wave dynamics was considered both in the kinetic and magnetohydrodynamic regimes. Up today only magnetohydrodynamic, phase-mixed, Gaussian Alfven pulses were investigated. In the present work we extend this into kinetic regime. Here phase-mixed, Gaussian Alfven pulses are studied, which are more appropriate for solar flares, than harmonic waves, as the flares are impulsive in nature. Collisionless, phase-mixed, dispersive, Gaussian Alfven pulse in transversely inhomogeneous plasma is investigated by particle-in-cell (PIC) simulations and by an analytical model. The pulse is in inertial regime with plasma beta less than electron-to-ion mass ratio and has a spatial width of 12 ion inertial length. The linear analytical model predicts that the pulse amplitude decrease is described by the linear Korteweg de Vries (KdV) equation. The numerical and analytical solution of the linear KdV equation produces the pulse amplitude decrease in time as t −1 . The latter scaling law is corroborated by full PIC simulations. It is shown that the pulse amplitude decrease is due to dispersive effects, while electron acceleration is due to Landau damping of the phase-mixed waves. The established amplitude decrease in time as t −1 is different from the MHD scaling of t −3/2 . This can be attributed to the dispersive effects resulting in the different scaling compared to MHD, where the resistive effects cause the damping, in turn, enhanced by the inhomogeneity. Reducing background plasma temperature and increase in ion mass yields more efficient particle acceleration.

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Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

Cited by 25 publications

References 37 publications

Non-propagating electric and density structures formed through non-linear interaction of Alfvén waves

Non-propagating electric and density structures formed through non-linear interaction of Alfvén waves

Electron trapping and acceleration by kinetic Alfvén waves in solar flares

Collisionless, phase-mixed, dispersive, Gaussian Alfven pulse in transversely inhomogeneous plasma

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