Thermal effects on ion-acoustic whistlers in the ionosphere in the presence of negative ions

1989 ◽  
Vol 67 (5) ◽  
pp. 457-462
Author(s):  
A. K. Sur
Keyword(s):  
Magnetic Field ◽  
Thermal Effects ◽  
Wave Amplitude ◽  
Negative Ions ◽  
Velocity Distribution Function ◽  
Space Plasma ◽  
Ion Acoustic ◽  
Comparison Of The Results ◽  
The Magnetic Field ◽  
Group Travel

In this paper, the thermal effects in the presence of negative ions are included in the evaluation of the group travel time of an ion-cyclotron whistler from its source to an observer in a satellite. The velocity distribution function and the relative wave amplitude of the magnetic field have been estimated theoretically from the cyclotron damping of the whistlers. Comparison of the results with those of Das et al. and Das and Sur shows that negative ions and thermal effects have important contributions to the propagation of whistlers in the ionosphere. An outline of possible applications is given for the study of space plasma problems.

scholarly journals Some aspects of ion-acoustic whistlers in the ionosphere in the presence of negative ions

1989 ◽  
Vol 12 (4) ◽  
pp. 749-772 ◽  
Author(s):  
A. K. Sur ◽  
G. C. Das ◽  
B. Chakraborty ◽  
S. N. Paul ◽  
L. Debnath
Keyword(s):  
Travel Time ◽  
Critical Frequency ◽  
Cyclotron Frequency ◽  
Negative Ions ◽  
Induced Magnetic Field ◽  
Ion Acoustic ◽  
Phase And Group Velocities ◽  
Group Velocities ◽  
Group Travel

A study is made of the propagation of ion-acoustic whistlers in the atmosphere including the effects of negative ions. The dispersion relation, phase and group velocities of whistlers are discussed. It is shown that the presence of negative ions introduces a critical frequency which, for equal ionic masses, is equal to the ion-cyclotron frequency. Special attention is given to the group travel time of whistlers at mid-latitude and equator so that the role of negative ions on the group travel time can be determined. The cyclotron damping of whistlers in the presence of negative ions has been studied. The velocity distribution, total attenuation and the induced magnetic field are calculated from the temporal as well as spatial cyclotron damping. It is suggested that the attenuation of whistlers may cause heating of the ionosphere. It is also indicated that the measurement of the group travel time from its source to the observer at the satellite would help to diagnose the ionospheric parameters. The results of the analysis are presented by several graphical presentations.

Magnetosonic solitons in space plasmas: dark or bright solitons?

2007 ◽  
Vol 73 (6) ◽  
pp. 981-992 ◽  
Author(s):  
O. A. POKHOTELOV ◽  
O.G. ONISHCHENKO ◽  
M. A. BALIKHIN ◽  
L. STENFLO ◽  
P. K. SHUKLA
Keyword(s):  
Magnetic Field ◽  
Distribution Function ◽  
Velocity Distribution Function ◽  
Mhd Equations ◽  
Space Plasmas ◽  
Ion Distribution ◽  
Loss Cone ◽  
Solitary Solution ◽  
Background Magnetic Field ◽  
The Magnetic Field

AbstractThe nonlinear theory of large-amplitude magnetosonic (MS) waves in highβ space plasmas is revisited. It is shown that solitary waves can exist in the form of ‘bright’ or ‘dark’ solitons in which the magnetic field is increased or decreased relative to the background magnetic field. This depends on the shape of the equilibrium ion distribution function. The basic parameter that controls the nonlinear structure is the wave dispersion, which can be either positive or negative. A general dispersion relation for MS waves propagating perpendicularly to the external magnetic field in a plasma with an arbitrary velocity distribution function is derived.It takes into account general plasma equilibria, such as the Dory–Guest–Harris (DGH) or Kennel–Ashour-Abdalla (KA) loss-cone equilibria, as well as distributions with a power-law velocity dependence that can be modelled by κdistributions. It is shown that in a bi-Maxwellian plasma the dispersion is negative, i.e. the phase velocity decreases with an increase of the wavenumber. This means that the solitary solution in this case has the form of a ‘bright’ soliton with the magnetic field increased. On the contrary, in some non-Maxwellian plasmas, such as those with ring-type ion distributions or DGH plasmas, the solitary solution may have the form of a magnetic hole. The results of similar investigations based on nonlinear Hall–MHD equations are reviewed. The relevance of our theoretical results to existing satellite wave observations is outlined.

Magnetic Field Analysis of the Actuator in a Semi-Active Vibration Control of the Beam with MR Fluid

2015 ◽  
Vol 759 ◽  
pp. 37-44
Author(s):  
Mateusz Romaszko ◽  
Łukasz Łacny
Keyword(s):  
Magnetic Field ◽  
Vibration Control ◽  
Field Distribution ◽  
Active Vibration Control ◽  
Magnetic Field Distribution ◽  
Field Analysis ◽  
Mr Fluid ◽  
Active Vibration ◽  
Comparison Of The Results ◽  
The Magnetic Field

In this study the analysis of the magnetic field distribution of an electromagnet is presented. This electromagnet is used as an actuator in a semi-active vibration control of the three-layer beam with MR fluid. Two separate numerical methods are used for the purpose of calculating the magnetic field distribution. The first method is based on the Finite Element Method and implemented using ANSYS software. The second, simplified one is based on the assumption that the electromagnet can be substituted by a simple magnetic circuit divided into separate paths, with each sub-path defined by the value of reluctance of the corresponding electromagnet part. The comparison of the results from both methods with the ones obtained from an experiment is also presented and analyzed in the paper.

scholarly journals Strong electromagnetic pulses generated in high-intensity short-pulse laser interactions with thin foil targets

2017 ◽  
Vol 35 (4) ◽  
pp. 677-686 ◽  
Author(s):  
P. Rączka ◽  
J.-L. Dubois ◽  
S. Hulin ◽  
V. Tikhonchuk ◽  
M. Rosiński ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Short Pulse ◽  
Thin Foil ◽  
Tangential Component ◽  
Laser Target ◽  
Electromagnetic Pulses ◽  
Target Interaction ◽  
Short Pulse Laser ◽  
Comparison Of The Results ◽  
The Magnetic Field

AbstractMeasurements are reported of the target neutralization current, the target charge, and the tangential component of the magnetic field generated as a result of laser–target interaction by pulses with the energy in the range of 45–92 mJ on target and the pulse duration from 39 to 1000 fs. The experiment was performed at the Eclipse facility in CELIA, Bordeaux. The aim of the experiment was to extend investigations performed for the thick (mm scale) targets to the case of thin (μm thickness) targets in a way that would allow for a straightforward comparison of the results. We found that thin foil targets tend to generate 20–50% higher neutralization current and the target charge than the thick targets. The measurement of the tangential component of the magnetic field had shown that the initial spike is dominated by the 1 ns pulse consistent with the 1 ns pulse of the neutralization current, but there are some differences between targets of different types on sub-ns scale, which is an effect going beyond a simple picture of the target acting as an antenna. The sub-ns structure appears to be reproducible to surprising degree. We found that there is in general a linear correlation between the maximum value of the magnetic field and the maximum neutralization current, which supports the target-antenna picture, except for pulses 100s of fs long.

Drift wave in the presence of a time varying inhomogeneous electric field

1983 ◽  
Vol 61 (7) ◽  
pp. 1099-1105 ◽  
Author(s):  
K. D. Misra ◽  
R. P. Pandey ◽  
M. S. Tiwari
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Space Plasma ◽  
Time Varying ◽  
Inhomogeneous Electric Field ◽  
Drift Wave ◽  
Plane Normal ◽  
Vlasov Equations ◽  
Drift Instability ◽  
The Magnetic Field

The drift instability has been studied in the presence of an inhomogeneous time varying electric field directed perpendicular to the impressed magnetic field in the presence of a magnetic field, and density and temperature gradients, using nonlinear particle trajectories in the Maxwell–Boltzmann–Vlasov equations. The dispersion relation and growth rate have been evaluated for the drift wave propagating obliquely to the magnetic field in a plane normal to a density gradient. The stabilization/destabilization of the drift wave by the inhomogeneous applied electric field has been discussed. The application of these results has been suggested for space plasma.

scholarly journals A peculiar form of low potential discharge in the highest vacua

1913 ◽  
Vol 89 (607) ◽  
pp. 68-74 ◽  
Keyword(s):  
Magnetic Field ◽  
Equatorial Plane ◽  
Negative Ions ◽  
Iron Electrodes ◽  
Glass Bulb ◽  
Peculiar Form ◽  
Principal Effect ◽  
Electrical Effect ◽  
Pointed End ◽  
The Magnetic Field

Mr. C. E. S. Phillips has described a curious electrical effect. Iron electordes E 1 , E 2 , fig. 1, were fixed in a glass bulb as shown. The bulb was exhausted very highly; a discharge was passed for a moment, and turned off. The iron electrodes were then magnetised by exciting the electromagnets M 1 , M 2 . On magnetisation, a luminous ring was observed in the equatorial plane of the magnet, which lasted for a few seconds, and then died out. The effect excited considerable interest at the time, and careful experiments were made by the discoverer to elucidate its causes. The following may be quoted from the concluding section of the paper as representing his views. “The preceding experiments show that the principal effect of the magnets is to produce a concentration of negative ions at the strongest portion of the magnetic field, and centrally within the bulb • • • • I consider that this concentration of negative ions is due to two main causes. In the first place it is partly produced by the action of the magnetic field on ions already in motion within the bulb • • • • • And secondly owing to the reaction resulting from the sudden excitation of the magnets, the comparatively dense cloud of ions situated at the ends of the bulb would, in rapidly turning about the magnetic axis, tend to move towards the pointed end of the electrodes, and so concentrate as observed.”

scholarly journals MULTI-PURPOSE MODES OF FORMATION OF ELECTRON BEAMS IN THE CYLINDRICAL MAGNETIC FIELD OF THE MAGNETRON GUN

2021 ◽  
pp. 45-49
Author(s):  
A.S. Mazmanishvili ◽  
N.G. Reshetnyak
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Electron Beam ◽  
Electron Beams ◽  
Electron Flow ◽  
Axial Direction ◽  
Beam Diameter ◽  
Transport Channel ◽  
Comparison Of The Results ◽  
The Magnetic Field

The results of the study on the formation of electron beams by the magnetron gun at various configurations of the magnetic field in the beam transport channel are presented. A technique for modeling the processes of formation of electron flows and control of the distribution of beams by collimation is presented. Numerical simulation of the dynamics of electron beams in the magnetic field of the gun for its various configurations has been carried out. Experimental data on the transportation and collimation of electron beams are presented. The possibility of stable formation of an electron beam in the axial direction during its transportation is shown. Imprints of the collimated electron beam were obtained on metal targets. The possibility of controlling the beam diameter by varying the magnetic field is shown. Comparison of the results of numerical modeling and experimental data on the motion and collimation of the tubular electron flow is carried out.

On the role of mother-planet magnetic field in spiral structure explanation of formation of spokes

1984 ◽  
Vol 75 ◽  
pp. 569-574
Author(s):  
G.X. Song
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Interplanetary Magnetic Field ◽  
Wave Amplitude ◽  
Spiral Structure ◽  
Dust Particles ◽  
Electromagnetic Effect ◽  
Sectoral Structure ◽  
The Magnetic Field

AbstractSome features about the spokes in B rings can be explained in terms of the electromagnetic effect. Due to the existence of the magnetic field in Saturn, plasma and micro-sized dust particles, the loosely spiral structure of magnetic field near Saturn, which is similar to that invoked to explain the sectoral structure of the interplanetary magnetic field in the solar system, may be induced.The spiral structure is rotating with mother-planet and will gradually form at corotation circle, but the wave amplitude will grow outside the corotation and will decay gradually inside the corotation. Using the characteristics of this spiral structure, we have tried to attack the mechanism of the formation of spokes.

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