Electrostatic noise bands associated with the electron gyrofrequency and plasma frequency in the outer magnetosphere

1975 ◽  
Vol 80 (31) ◽  
pp. 4259-4271 ◽  
Author(s):  
Robert R. Shaw ◽  
Donald A. Gurnett
Keyword(s):  
Plasma Frequency ◽  
Outer Magnetosphere ◽  
Electron Gyrofrequency

THE RESONANT FREQUENCIES OF CAVITIES IN A MAGNETOIONIC MEDIUM

1964 ◽  
Vol 42 (1) ◽  
pp. 90-102 ◽  
Author(s):  
K. G. Budden
Keyword(s):  
Plasma Frequency ◽  
Space Vehicle ◽  
Boundary Region ◽  
Plasma Sheath ◽  
Space Vehicles ◽  
Isotropic Plasma ◽  
Resonant Frequencies ◽  
Characteristic Frequencies ◽  
Spherical Mass ◽  
Electron Gyrofrequency

The resonant frequencies for a hollow cylindrical or spherical cavity in a magnetoionic medium are derived using a simple model in which the boundary of the cavity is sharp and the medium outside it is homogeneous and loss free, but anisotropic. The effects of electron temperature and of nonlinearity are ignored. The problem is complementary to a similar problem treated by Herlofsen (1951), who discussed the resonant frequencies of a uniform cylindrical or spherical mass of isotropic plasma surrounded by a vacuum. It is found that the resonant frequencies are not equal to the characteristic frequencies of the plasma as usually described by the formulae X = 1, X = 1 ± Y, but are more complicated functions of the plasma frequency and the electron gyrofrequency. It is concluded that, for a plasma sheath or cavity of any structure, with a sharp or gradual boundary region, the resonant frequencies will in general differ from the characteristic frequencies of the undisturbed plasma. For a cylindrical cavity the resonant frequencies depend upon the angle between the axis of the cavity and the constant magnetic field. The results may have applications to the interpretation of plasma "spikes" observed with space vehicles, and to the theory of the radar cross section of a space vehicle within the ionosphere.

Excitation of the plasma and upper hybrid resonances in a warm magnetoplasma by an alternating electric dipole

1974 ◽  
Vol 11 (2) ◽  
pp. 225-252 ◽  
Author(s):  
J. M. Chassériaux
Keyword(s):  
Magnetic Field ◽  
Electric Dipole ◽  
Plasma Frequency ◽  
Cylindrical Wave ◽  
The Other ◽  
Mutual Impedance ◽  
Adiabatic Theory ◽  
Hybrid Frequency ◽  
Equipotential Surfaces ◽  
Electron Gyrofrequency

The potential created by an alternating dipole in a warm magnetoplasma is calculated analytically, in the approximation of the full adiabatic theory, for excitation frequencies ω close either to the upper hybrid frequency ωT or to the plasma frequency ωp The potential is finite at these frequencies. For ω ˜ ωp, the equipotential surfaces can be considered roughly as planes perpendicular to the static magnetic field B. For ω ˜ ωT and ω2p ≪3ω2b (where ωb is the electron gyrofrequency), the equipotential surfaces are cylinders of axis B. On the other hand, if ω2p ≪3ω2b, the potential is the sum of a cylindrical wave and of a wave for which the equipotential surfaces are paraboloids of axis B. These results are used to calculate the mutual impedance ζ of a quadrupole probe, and it is shown that the measurement of Zγ atω = ωT provides a new method for determining the electron temperature.

Untersuchung über die Ausbreitung von elektromagnetischen Wellen in einem zylindrischen Plasma mit Magnetfeld

1967 ◽  
Vol 22 (10) ◽  
pp. 1592-1599 ◽  
Author(s):  
Karl Weinhardt
Keyword(s):  
Maxwell Equations ◽  
Plasma Frequency ◽  
Arc Discharge ◽  
Collisionless Plasma ◽  
Electron Plasma ◽  
Coupling System ◽  
Field Lines ◽  
Cathode Arc ◽  
Electron Gyrofrequency ◽  
The Magnetic Field

Propagation of circularly symmetric electromagnetic modes parallel to the magnetic field lines in the positive column of an argon hollow-cathode arc discharge has been studied. The applied frequency (3·109 cps) was less than both the electron gyrofrequency and the electron plasma frequency. These measurements were compared with dispersion relations for circulary symmetric modes calculated by using the complete MAXWELL equations, the ε-tensor for a cold collisionless plasma, and suitable boundary conditions. It could be shown that the mode which was excited was most likely determined by the boundary of the coupling system and not by the boundary of the whole vessel as originally expected.

An analytical study of the oblique echo model for the topside plasma resonance

1974 ◽  
Vol 12 (2) ◽  
pp. 199-216 ◽  
Author(s):  
E. J. Parkes
Keyword(s):  
Electric Field ◽  
Saddle Point ◽  
Analytical Study ◽  
Plasma Frequency ◽  
Strong Resonance ◽  
Electron Density Gradient ◽  
Resonance Solution ◽  
Weak Resonance ◽  
Electron Gyrofrequency ◽  
Observation Times

The oblique echo model for the resonance near the local plasma frequency fN observed by topside sounders involves the propagation of slow waves away from the sounder, which later return as echoes after reflexion due to an electron density gradient. The model is investigated using the WKB technique introduced by Fejer & Yu. The resulting set of saddle-point equations is solved by a method which can, unlike previous work, be applied to both the ‘strong’ resonance (for whichfN > fH wherefH is the electron gyrofrequency) and to the ‘weak’ (fN < fH) resonance. Throughout the calculations, the validity of the approximations made is checked. It is found that the weak resonance solution is not valid for typical topside parameters. For the strong resonance, the electric field of a small pulsed dipole is calculated. Expressions are found for the frequency of the two echoes that are received by the sounder and the frequency of the beating between them. Although these are only strictly valid for times longer than typical observation times, they yield results that agree well with the corresponding results from ray trajectory computations.

Generation of Bernstein modes in space and laboratory plasmas by injection of an electron beam

1997 ◽  
Vol 57 (2) ◽  
pp. 387-401 ◽  
Author(s):  
GEORGYI V. LIZUNOV
Keyword(s):  
Electron Beam ◽  
Hydrodynamic Interaction ◽  
Plasma Frequency ◽  
Spectral Maximum ◽  
Vacuum Chambers ◽  
Translational Movement ◽  
Laboratory Plasmas ◽  
Hybrid Plasma ◽  
Beam Interaction ◽  
Electron Gyrofrequency

The theory of electron-beam interaction with Bernstein plasma modes is developed for conditions of active space plasma experiments as well as experiments in large vacuum chambers. Translational movement of the beam along a magnetic field and Larmor rotation of the beam are considered as sources of free energy for wave build-up. Part of the energy of translational movement is lost to the excitation of Langmuir plasma oscillations. Bernstein modes then slowly grow owing to a ‘fan’-type instability. In this case the emission spectrum consists of lines near the half-harmonics of the electron gyrofrequency, ≈(n+½)ωc. Larmor gyration of the beam is not destroyed by the excitation of Langmuir turbulence, and thus there is strong hydrodynamic interaction of the rotated beam with the Bernstein modes. Integer harmonics of gyrofrequency nωc are generated in this case, with the spectral maximum near the upper-hybrid plasma frequency.

Whistler-mode propagation at frequencies near the electron gyrofrequency

1983 ◽  
Vol 29 (2) ◽  
pp. 217-222 ◽  
Author(s):  
S. S. Sazhin
Keyword(s):  
Magnetic Field ◽  
Plasma Frequency ◽  
Electron Plasma ◽  
Dispersion Function ◽  
Frequency Interval ◽  
Mode Propagation ◽  
Whistler Mode ◽  
Graphical Technique ◽  
Electron Gyrofrequency ◽  
Plasma Dispersion

Parallel whistler-mode propagation in a hot anisotropic plasma at frequencies near the electron gyrofrequency is considered by using analytical methods and a simple graphical technique, without any special restrictions on the value of the imaginary part of the plasma dispersion function argument. An exact criterion for the possibility of whistler-mode propagation in the vicinity of the electron gyrofrequency is derived. In particular it is pointed out that whistlers in this frequency interval can propagate only in a very hot and rarefied plasma submerged in a strong magnetic field. These whistlers can only be damped, the modulus of the decrement of the damping cannot exceed 1·1 times the electron plasma frequency. The refractive index remains close to unity.

scholarly journals Chorus source region localization in the Earth's outer magnetosphere using THEMIS measurements

2010 ◽  
Vol 28 (6) ◽  
pp. 1377-1386 ◽  
Author(s):  
O. Agapitov ◽  
V. Krasnoselskikh ◽  
Yu. Zaliznyak ◽  
V. Angelopoulos ◽  
O. Le Contel ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Source Region ◽  
Phase Correlation ◽  
Local Magnetic Field ◽  
Localized Source ◽  
Poynting Flux ◽  
Outer Magnetosphere ◽  
Vector Distribution ◽  
Field Lines ◽  
Electron Gyrofrequency

Abstract. Discrete ELF/VLF chorus emissions, the most intense electromagnetic plasma waves observed in the Earth's radiation belts and outer magnetosphere, are thought to propagate roughly along magnetic field lines from a localized source region near the magnetic equator towards the magnetic poles. THEMIS project Electric Field Instrument (EFI) and Search Coil Magnetometer (SCM) measurements were used to determine the spatial scale of the chorus source localization region on the day side of the Earth's outer magnetosphere. We present simultaneous observations of the same chorus elements registered onboard several THEMIS spacecraft in 2007 when all the spacecraft were in the same orbit. Discrete chorus elements were observed at 0.15–0.25 of the local electron gyrofrequency, which is typical for the outer magnetosphere. We evaluated the Poynting flux and wave vector distribution and obtained chorus wave packet quasi-parallel propagation to the local magnetic field. Amplitude and phase correlation data analysis allowed us to estimate the characteristic spatial correlation scale transverse to the local magnetic field to be in the 2800–3200 km range.

Plasma frequency determination in YBa2Cu3O6+x as a function of oxygen content

1989 ◽  
Vol 50 (18) ◽  
pp. 2895-2901 ◽  
Author(s):  
N. Bontemps ◽  
D. Fournier ◽  
A.C. Boccara ◽  
P. Monod ◽  
H. Alloul ◽  
...  
Keyword(s):  
Oxygen Content ◽  
Plasma Frequency ◽  
Frequency Determination

scholarly journals LHR effects in nonducted whistler propagation – new observations and numerical modelling

2001 ◽  
Vol 19 (2) ◽  
pp. 147-157 ◽  
Author(s):  
F. Jiřiček ◽  
D. R. Shklyar ◽  
P. Třiska
Keyword(s):  
Wave Propagation ◽  
Numerical Modelling ◽  
Plasma Frequency ◽  
Cutoff Frequency ◽  
Lower Hybrid ◽  
Noise Band ◽  
Maximum Value ◽  
Lower Hybrid Resonance ◽  
Whistler Propagation ◽  
Lower Cutoff

Abstract. VLF-ELF broadband measurements onboard the MAGION 4 and 5 satellites at heights above 1 Re in plasmasphere provide new data on various known phenomena related to ducted and nonducted whistler wave propagation. Two examples are discussed: magnetospherically reflected (MR) whistlers and lower hybrid resonance (LHR) noise band. We present examples of rather complicated MR whistler spectrograms not reported previously and argue the conditions for their generation. Analytical consideration, together with numerical modelling, yield understanding of the main features of those spectrograms. LHR noise band, as well as MR whistlers, is a phenomenon whose source is the energy propagating in the nonducted way. At the plasmaspheric heights, where hydrogen (H+) is the prevailing ion, and electron plasma frequency is much larger than gyrofrequency, the LHR frequency is close to its maximumvalue in a given magnetic field. This frequency is well followed by the observed noise bands. The lower cutoff frequency of this band is somewhat below that maximum value. The reason for this, as well as the possibility of using the LHR noise bands for locating the plasma through position, are discussed.Key words. Magnetospheric physics (plasmasphere; wave propagation)

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