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

2012 ◽  
Vol 30 (1) ◽  
pp. 81-95 ◽  
Author(s):  
F. Mottez
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Plasma Density ◽  
Homogeneous Medium ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Magnetic Field Direction ◽  
Linear Interaction ◽  
Ambient Magnetic Field ◽  
Non Linear

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.

On nonlinear circularly polarized Alfvén waves

1988 ◽  
Vol 40 (2) ◽  
pp. 281-287 ◽  
Author(s):  
G. Mann
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Periodic Solutions ◽  
Type Equation ◽  
Finite Amplitude ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Circularly Polarized ◽  
Ambient Magnetic Field ◽  
Nonlinear Schrödinger

Finite-amplitude circularly polarized Alfvén waves propagating along the ambient magnetic field are described by a derivative nonlinear Schrödinger-type equation. It leads to stationary, solitary and periodic solutions with phase modulations. The amplitude–width relation for these solitons is shown to be an inequality. The relevance of the results is briefly discussed for particular phenomena in the solar wind.

scholarly journals Electric fields and double layers in plasmas

1987 ◽  
Vol 5 (2) ◽  
pp. 233-255 ◽  
Author(s):  
Nagendra Singh ◽  
H. Thiemann ◽  
R. W. Schunk
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Electric Fields ◽  
Sheet Thickness ◽  
High Density ◽  
Effective Length ◽  
Double Layers ◽  
Low Density ◽  
Ambient Magnetic Field ◽  
Cold Plasmas

Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamic features of the double layers are discussed. These features, as seen in simulations, laboratory experiments and theory, indicate that double layers and the currents through them undergo slow oscillations, which are determined by the ion transit time across an effective length of the system in which the double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations have been considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields (parallel to an ambient magnetic field) and double layers in an expanding plasma are discussed.

scholarly journals Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves

2015 ◽  
Vol 120 (12) ◽  
pp. 10,384-10,403 ◽  
Author(s):  
Kazue Takahashi ◽  
Colin Waters ◽  
Karl-Heinz Glassmeier ◽  
Craig A. Kletzing ◽  
William S. Kurth ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Toroidal Mode

Concerning the Dynamics of Energetic Protons in Coronal Magnetic Loops: Dispersion Effects of Alfven Waves

1985 ◽  
Vol 107 ◽  
pp. 559-559
Author(s):  
V. A. Mazur ◽  
A. V. Stepanov
Keyword(s):  
Magnetic Field ◽  
Wave Dispersion ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Wave Number ◽  
Alfvén Waves ◽  
Coronal Loops ◽  
Coronal Magnetic Loops ◽  
The Magnetic Field ◽  
Solar Coronal

It is shown that the existence of plasma density inhomogeneities (ducts) elongated along the magnetic field in coronal loops, and of Alfven wave dispersion, associated with the taking into account of gyrotropy U ≡ ω/ωi ≪ 1 (Leonovich et al., 1983), leads to the possibility of a quasi-longitudinal k⊥ < √U k‖ propagation (wave guiding) of Alfven waves. Here ω is the frequency of Alfven waves, ωi is the proton gyrofrequency, and k is the wave number. It is found that with the parameter ξ = ω2 R/ωi A > 1, where R is the inhomogeneity scale of a loop across the magnetic field, and A is the Alfven wave velocity, refraction of Alfven waves does not lead, as contrasted to Wentzel's inference (1976), to the waves going out of the regime of quasi-longitudinal propagation. As the result, the amplification of Alfven waves in solar coronal loops can be important. A study is made of the cyclotron instability of Alfven waves under solar coronal conditions.

scholarly journals Alfvén Waves in Dusty Interstellar Clouds

1997 ◽  
Vol 14 (2) ◽  
pp. 170-178 ◽  
Author(s):  
N. F. Cramer ◽  
S. V. Vladimirov
Keyword(s):  
Magnetic Field ◽  
Negative Charge ◽  
Alfven Waves ◽  
Dust Particles ◽  
Alfvén Waves ◽  
Interstellar Clouds ◽  
General Dispersion ◽  
The Right ◽  
The Magnetic Field ◽  
Field Wave

AbstractDust particles in a plasma can be higWy charged, and can carry a proportion of the negative charge of the plasma. Even if this proportion is quite small, as in interstellar dusty clouds, it can have a large effect on hydromagnetic Alfvén waves propagating at frequencies well below the ion–cyclotron frequency. In particular, the right-hand circularly polarised mode experiences a cutoff due to the presence of the dust. We generalise previous work on Alfvén waves in dusty interstellar plasmas by considering the general dispersion relation for waves propagating at an arbitrary angle with respect to the magnetic field. Wave energy propagating at oblique angles to the magnetic field in an increasing density gradient can be very efficiently damped by the Alfvén resonance absorption process in a dusty plasma, and we consider this damping mechanism for waves in interstellar clouds.

Sign in / Sign up

Export Citation Format

Share Document