Propagation of hydromagnetic waves normal to the magnetic field in the presence of currents

1969 ◽  
Vol 17 (2) ◽  
pp. 247-254 ◽  
Author(s):  
M. Abbas
Keyword(s):  
Magnetic Field ◽  
Hydromagnetic Waves ◽  
The Magnetic Field

Absorption of hydromagnetic waves in the ionosphere

1970 ◽  
Vol 48 (3) ◽  
pp. 362-366
Author(s):  
M. Abbas
Keyword(s):  
Magnetic Field ◽  
Frequency Range ◽  
Parallel Propagation ◽  
Hydromagnetic Waves ◽  
The Magnetic Field

Absorption of hydromagnetic waves in the ionosphere propagated normal to the magnetic field is calculated at various frequencies and compared with the absorption for parallel propagation. Data corresponding to both daytime and nighttime ionospheres are used. Waves propagated normal to the magnetic field are highly absorbed through the daytime ionosphere at frequencies above a few Hz; the nighttime ionosphere, however, is virtually transparent to waves in the frequency range of 10−3 to 20 Hz. A comparison of the absorption processes for waves propagated parallel and normal to the magnetic field is made.

Resonantly unstable off-angle hydromagnetic waves

1967 ◽  
Vol 1 (1) ◽  
pp. 81-104 ◽  
Author(s):  
C. F. Kennel ◽  
H. V. Wong
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Electrostatic Waves ◽  
High Energy Tail ◽  
Electrons And Ions ◽  
Ion Cyclotron ◽  
Cold Component ◽  
Hydromagnetic Waves ◽  
The Magnetic Field ◽  
Uniform Plasma

We consider semi-quantitatively the cyclotron resonance instability of ion cyclotron and magnetosonic waves propagating at an angle to the magnetic field in an infinite uniform plasma. The velocity distributions of electrons and ions consist of a dense cold component and a diffuse high-energy tail. If the high-energy protons are sufficiently intense and their pitch angle distributions sufficiently anisotropic, instability occurs for those waves propagating parallel to the magnetic field. If the spectrum of resonant protons is sufficiently hard, a reasonably large cone of propagating angles about the magnetic field can be unstable. Observed fluxes of trapped protons in the magnetosphere should destabilise the ion cyclotron wave at a lower intensity threshold than for at least one class of electrostatic waves.

Ergodic behaviour of nonlinear hydromagnetic waves in a cold collisionless plasma

1972 ◽  
Vol 8 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Youshinori Inoue ◽  
Noriaki Kimura
Keyword(s):  
Magnetic Field ◽  
Phase Plane ◽  
Measure Zero ◽  
Irrational Number ◽  
Collisionless Plasma ◽  
Analytical Dynamics ◽  
Hydromagnetic Waves ◽  
The Waves ◽  
The Magnetic Field ◽  
Ergodic Behaviour

Nonlinear hydromagnetic waves propagating along a magnetic field in a cold collisionless plasma are investigated. A criterion for ergodicity of the waves is obtained using the usual method of analytical dynamics. According to this criterion, it is found that, if a parameter b00 is a rational number, the wave is periodic, and that, if b00 is an irrational number, the wave is ergodic. Therefore, the waves are almost always ergodic, i.e. the trajectory of the wave fills up a region in the phase plane of the magnetic field. On the other hand, periodic solutions can exist only with measure zero.

scholarly journals Propagation of a solitary wave along a magnetic field in a cold collision-free plasma

1961 ◽  
Vol 11 (1) ◽  
pp. 16-20 ◽  
Author(s):  
P. G. Saffman
Keyword(s):  
Magnetic Field ◽  
Geometric Mean ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Order Of Magnitude ◽  
Hydromagnetic Waves ◽  
Cold Collision ◽  
The Magnetic Field ◽  
Free Plasma ◽  
Alfven Velocity

It is shown that solitary hydromagnetic waves can propagate parallel to a uniform magnetic field in a cold collision-free plasma. These waves are exact solutions of the non-linear equations of motion except for the quasi-neutral approximation. The velocity of propagation lies in a range of values somewhat larger than the Alfvén velocity, and is of the order of 25 times the Alfvén velocity for hydrogen, the precise value depending upon the strength of the wave. Simple expressions exist for the velocities of the ions and electrons and the magnetic field inside the wave. The lines of force are spirals about the direction of propagation. The waves are symmetrical about their middle. The order of magnitude of their width is the geometric mean of the gyro-radii of the ions and electrons when moving with the Alfvén velocity. The maximum value of the magnetic field can be somewhat larger than the value away from the wave.

The effect of lower-hybrid waves on the propagation of hydromagnetic waves

1988 ◽  
Vol 40 (2) ◽  
pp. 337-351
Author(s):  
Hiromitsu Hamabata ◽  
Tomikazu Namikawa ◽  
Kazuhiro Mori
Keyword(s):  
Magnetic Field ◽  
Phase Speed ◽  
Density Perturbation ◽  
Propagation Direction ◽  
Lower Hybrid ◽  
Hydromagnetic Waves ◽  
Hybrid Waves ◽  
Lower Hybrid Waves ◽  
Magnetic Plasma ◽  
The Magnetic Field

Propagation characteristics of hydromagnetic waves in a magnetic plasma are investigated using the two-plasma fluid equations including the effect of lower-hybrid waves propagating perpendicularly to the magnetic field. The effect of lower-hybrid waves on the propagation of hydromagnetic waves is analysed in terms of phase speed, growth rate, refractive index, polarization and the amplitude relation between the density perturbation and the magnetic-field perturbation for the cases when hydromagnetic waves propagate in the plane whose normal is perpendicular to both the magnetic field and the propagation direction of lower-hybrid waves and in the plane perpendicular to the propagation direction of lower-hybrid waves. It is shown that hydromagnetic waves propagating at small angles to the propagation direction of lower-hybrid waves can be excited by the effect of lower-hybrid waves and the energy of excited waves propagates nearly parallel to the propagation direction of lower-hybrid waves.

scholarly journals On the Hydromagnetic Stability of Fluid Rotating between Two Concentric Cylinders

1970 ◽  
Vol 30 ◽  
pp. 41-50
Author(s):  
Hosne Ara Jasmine
Keyword(s):  
Magnetic Field ◽  
Theoretical Study ◽  
Stability Conditions ◽  
Governing Equations ◽  
Magnetic Field Profile ◽  
Hydromagnetic Instability ◽  
Concentric Cylinders ◽  
Wide Range ◽  
Hydromagnetic Waves ◽  
The Magnetic Field

A theoretical study of the hydromagnetic instability due to slow hydromagnetic waves has been carried out after simplifying the complexity of governing equations. A series of stability conditions have been derived for wide range of magnetic field profiles. It has been shown that regardless of the magnetic field profile, any unstable disturbances propagate against the basic rotation. GANIT J. Bangladesh Math. Soc. (ISSN 1606-3694) 30 (2010) 41-50  DOI: http://dx.doi.org/10.3329/ganit.v30i0.8502

Hydromagnetic waves in a finitely conducting fluid mass immersed in a nonuniform magnetic field

1969 ◽  
Vol 47 (9) ◽  
pp. 1011-1016
Author(s):  
G. S. Bajwa ◽  
K. M. Srivastava
Keyword(s):  
Magnetic Field ◽  
Coordinate System ◽  
Inhomogeneous Magnetic Field ◽  
Constant Density ◽  
Curvilinear Coordinate System ◽  
Fluid Mass ◽  
Curvilinear Coordinate ◽  
Hydromagnetic Waves ◽  
The Magnetic Field ◽  
Lines Of Force

We have studied the propagation of hydromagnetic waves in a finitely conducting, nonviscous fluid mass of constant density. It is immersed in a time-independent inhomogeneous magnetic field. Due to the nonuniformity of the magnetic field the lines of force are not in general straight lines, and we have made use of a general curvilinear coordinate system. The lines of force of the magneticfield are taken as the coordinate lines and the propagation of hydromagnetic waves is explored. In the discussion we have chosen symmetry with respect to the binormal to the osculating plane containing lines of force, and the lines of force are assumed to be torsionless which make the curvilinear coordinate system orthogonal. By taking binormal as the z axis of the Cartesian coordinate system we conclude that Alfven waves propagate along the field lines and the local inhomogeneity of the magnetic field causes damping of the waves.

On the modulational instability of hydromagnetic waves parallel to the magnetic field

1976 ◽  
Vol 16 (3) ◽  
pp. 321-334 ◽  
Author(s):  
Einar Mjølhus
Keyword(s):  
Magnetic Field ◽  
Stability Condition ◽  
Modulational Instability ◽  
Finite Amplitude ◽  
Circularly Polarized ◽  
Polarized Waves ◽  
Arbitrary Amplitude ◽  
The Stability ◽  
Hydromagnetic Waves ◽  
The Magnetic Field

The stability of circularly polarized waves of finite amplitude propagating parallel to the magnetic field is studied. A set of equations for slowly varying waves of arbitrary amplitude is obtained. A discussion of the stability of the waces is based on this set of equations. Earlier results are confirmed; in addition we find that finite amplitude always promotes stability. An amplitude dependent stability condition for long waves, previously obtained by the author, is confirmed.

On the hydromagnetic stability of a rotating fluid annulus

1972 ◽  
Vol 52 (3) ◽  
pp. 529-541 ◽  
Author(s):  
D. J. Acheson
Keyword(s):  
Magnetic Field ◽  
Rotation Speed ◽  
Recent Theory ◽  
Rotating Fluid ◽  
Geomagnetic Secular Variation ◽  
Axis Of Rotation ◽  
Dissipative Fluid ◽  
Hydromagnetic Waves ◽  
Axisymmetric Disturbances ◽  
The Magnetic Field

A non-dissipative fluid rotates uniformly in the annular region between two infinitely long cylinders and is permeated by a magnetic field varying with distance from the axis of rotation. The hydromagnetic stability of this system is examined theoretically. When the magnetic field is azimuthal the system can always be rendered stable to axisymmetric disturbances by sufficiently rapid rotation (Michael 1954). Unless the magnetic field everywhere decreases with radius, however, the system may be unstable to non-axisymmetric disturbances even when the rotation speed exceeds a typical Alfvén speed by many orders of magnitude. ‘Slow’ hydromagnetic waves, akin to those invoked in a recent theory of the geomagnetic secular variation (Hide 1966), may then be generated by the spatial variations of the magnetic field. All unstable waves so generated propagate against the basic rotation, i.e. ‘westward’, when the field is azimuthal, and this property is in fact remarkably insensitive to variations in both magnitude and direction of the imposed field.

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