Определение локализации альфвеновских колебаний в плазме токамака ТУМАН-3М

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.

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900076105 ◽

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.

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The Effect of the Magnetic Field on the Rayleigh-Taylor Instability in a Couple-Stress Fluid

International Journal of Applied Mechanics and Engineering ◽

10.2478/ijame-2018-0033 ◽

2018 ◽

Vol 23 (3) ◽

pp. 611-622

Author(s):

K.B. Chavaraddi ◽

V.B. Awati ◽

M.M. Nandeppanavar ◽

P.M. Gouder

Keyword(s):

Magnetic Field ◽

Growth Rate ◽

Dispersion Relation ◽

Boundary Conditions ◽

Couple Stress ◽

Taylor Instability ◽

Wave Number ◽

Special Cases ◽

Rayleigh Taylor Instability ◽

The Magnetic Field

Abstract In this study we examine the effect of the magnetic field parameter on the growth rate of the Rayleigh-Taylor instability (RTI) in a couple stress fluids. A simple theory based on fully developed flow approximations is used to derive the dispersion relation for the growth rate of the RTI. The general dispersion relation obtained using perturbation equations with appropriate boundary conditions will be reduced for the special cases of propagation and the condition of instability and stability will be obtained. In solving the problem of the R-T instability the appropriate boundary conditions will be applied. The couple-stress parameter is found to be stabilizing and the influence of the various parameters involved in the problem on the interface stability is thoroughly analyzed. The new results will be obtained by plotting the curves between the dimensionless growth rate and the dimensionless wave number for various physical parameters involved in the problem (viz. the magnetic field, couple-stress, porosity, etc.) in the problem. It is found that the magnetic field and couple-stress have a stabilization effect whereas the buoyancy force (surface tension) has a destabilization effect on the RT instability in the presence of porous media.

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Untersuchung des Druckaufbaus einer stationären, magnetfeldstabilisierten Helium-Entladung mit Hilfe magnetischer Messungen

Zeitschrift für Naturforschung A ◽

10.1515/zna-1967-1023 ◽

1967 ◽

Vol 22 (10) ◽

pp. 1599-1612 ◽

Cited By ~ 2

Author(s):

Otto Klüber

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Plasma Column ◽

Ambipolar Diffusion ◽

Nernst Effect ◽

Thermomagnetic Effect ◽

Field Coil ◽

Neutral Gas ◽

Ring Currents ◽

The Magnetic Field

A stationary discharge is produced bya current flowing parallel to the magnetic field ofa cylindrical coil. In the region where the field is homogeneous the pressure in the plasma column is much higher than that in the surrounding neutral gas. This is mainly caused by diamagnetic ring currents, as is shown by measuring the magnetic flux due to these currents. Two effects are primarily responsible for the ring currents in this region: The already known effect of the ambipolar diffusion across the magnetic field anda thermomagnetic effect, called NERNST effect, whose influence on the pressure build-up ofa plasma has not been investigated hitherto. Other phenomena causing ring currents occur in the plasma near the coil ends and outside the field coil.

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The influence of resistivity gradients on shock conditions for a Petschek reconnection geometry

Annales Geophysicae ◽

10.5194/angeo-34-421-2016 ◽

2016 ◽

Vol 34 (4) ◽

pp. 421-425

Author(s):

Christian Nabert ◽

Karl-Heinz Glassmeier

Keyword(s):

Magnetic Field ◽

Necessary Conditions ◽

The Other ◽

Diffusion Region ◽

Two Dimensional ◽

Characteristic Velocity ◽

Magnetohydrodynamic Equations ◽

One Dimensional ◽

The Magnetic Field ◽

Alfven Velocity

Abstract. Shock waves can strongly influence magnetic reconnection as seen by the slow shocks attached to the diffusion region in Petschek reconnection. We derive necessary conditions for such shocks in a nonuniform resistive magnetohydrodynamic plasma and discuss them with respect to the slow shocks in Petschek reconnection. Expressions for the spatial variation of the velocity and the magnetic field are derived by rearranging terms of the resistive magnetohydrodynamic equations without solving them. These expressions contain removable singularities if the flow velocity of the plasma equals a certain characteristic velocity depending on the other flow quantities. Such a singularity can be related to the strong spatial variations across a shock. In contrast to the analysis of Rankine–Hugoniot relations, the investigation of these singularities allows us to take the finite resistivity into account. Starting from considering perpendicular shocks in a simplified one-dimensional geometry to introduce the approach, shock conditions for a more general two-dimensional situation are derived. Then the latter relations are limited to an incompressible plasma to consider the subcritical slow shocks of Petschek reconnection. A gradient of the resistivity significantly modifies the characteristic velocity of wave propagation. The corresponding relations show that a gradient of the resistivity can lower the characteristic Alfvén velocity to an effective Alfvén velocity. This can strongly impact the conditions for shocks in a Petschek reconnection geometry.

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Influence of the magnetic field of stellar wind on hot jupiter’s envelopes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000083 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 268-279

Author(s):

Dmitry V. Bisikalo ◽

Andrey G. Zhilkin

Keyword(s):

Magnetic Field ◽

Plasma Flow ◽

Coronal Mass Ejections ◽

Stellar Wind ◽

Roche Lobe ◽

Bow Shock ◽

Hot Jupiters ◽

The Magnetic Field ◽

Alfven Velocity ◽

Hot Jupiter

AbstractHot Jupiters have extended gaseous (ionospheric) envelopes, which extend far beyond the Roche lobe. The envelopes are loosely bound to the planet and, therefore, are strongly influenced by fluctuations of the stellar wind. We show that, since hot Jupiters are close to the parent stars, magnetic field of the stellar wind is an important factor defining the structure of their magnetospheres. For a typical hot Jupiter, velocity of the stellar wind plasma flow around the atmosphere is close to the Alfvén velocity. As a result stellar wind fluctuations, such as coronal mass ejections, can affect the conditions for the formation of a bow shock around a hot Jupiter. This effect can affect observational manifestations of hot Jupiters.

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Magnetic Rayleigh–Taylor instability at a contact discontinuity with an oblique magnetic field

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936490 ◽

2020 ◽

Vol 634 ◽

pp. A96

Author(s):

E. Vickers ◽

I. Ballai ◽

R. Erdélyi

Keyword(s):

Magnetic Field ◽

Growth Rate ◽

Dispersion Relation ◽

Contact Discontinuity ◽

Homogeneous Magnetic Field ◽

Taylor Instability ◽

Wide Range ◽

Rayleigh Taylor Instability ◽

The Magnetic Field ◽

Theoretical Results

Aims. We investigate the nature of the magnetic Rayleigh–Taylor instability at a density interface that is permeated by an oblique homogeneous magnetic field in an incompressible limit. Methods. Using the system of linearised ideal incompressible magnetohydrodynamics equations, we derive the dispersion relation for perturbations of the contact discontinuity by imposing the necessary continuity conditions at the interface. The imaginary part of the frequency describes the growth rate of waves due to instability. The growth rate of waves is studied by numerically solving the dispersion relation. Results. The critical wavenumber at which waves become unstable, which is present for a parallel magnetic field, disappears because the magnetic field is inclined. Instead, waves are shown to be unstable for all wavenumbers. Theoretical results are applied to diagnose the structure of the magnetic field in prominence threads. When we apply our theoretical results to observed waves in prominence plumes, we obtain a wide range of field inclination angles, from 0.5° up to 30°. These results highlight the diagnostic possibilities that our study offers.

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Alfvén Waves in Dusty Interstellar Clouds

Publications of the Astronomical Society of Australia ◽

10.1071/as97170 ◽

1997 ◽

Vol 14 (2) ◽

pp. 170-178 ◽

Cited By ~ 15

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.

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Photons in a cold axion background and strong magnetic fields: Polarimetric consequences

International Journal of Modern Physics A ◽

10.1142/s0217751x15500992 ◽

2015 ◽

Vol 30 (17) ◽

pp. 1550099 ◽

Cited By ~ 6

Author(s):

Domènec Espriu ◽

Albert Renau

Keyword(s):

Magnetic Field ◽

Dark Matter ◽

Galactic Halo ◽

Local Density ◽

Polarization Plane ◽

Strong Magnetic Fields ◽

Two Photon ◽

Main Effect ◽

Optical Table ◽

The Magnetic Field

In this work, we analyze the propagation of photons in an environment where a strong magnetic field (perpendicular to the photon momenta) coexists with an oscillating cold axion background with the characteristics expected from dark matter in the galactic halo. Qualitatively, the main effect of the combined background is to produce a three-way mixing among the two photon polarizations and the axion. It is interesting to note that in spite of the extremely weak interaction of photons with the cold axion background, its effects compete with those coming from the magnetic field in some regions of the parameter space. We determine (with one plausible simplification) the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments.

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