Ion sheath effects near antennas radiating within the ionosphere

Whale, H. A.

doi:10.1029/jz069i003p00447

Cited by 22 publications

(13 citation statements)

References 3 publications

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“…During the rf pulse, the Lorentz force and the induced dc sheath potential combine to force electrons into large-amplitude orbits centered near the sheath plasma interface [Whale, 1964;Laframboise et al, 1975]. Individual particle orbits are described by equation (1) in which Ea is augmented by a dc field term which tends to keep electrons near the sheath [Whale, 1964]. The sheath limit oscillates at the radio frequency.…”

Section: The Electron Flux Varies As (Energymentioning

confidence: 99%

Section: On the Basis Of The Vacuum Dipole Theory B•r At A Distance mentioning

confidence: 99%

“…In an isotropic plasma, Whale [1964] Also, note that collective oscillations of a hot plasma in a cylindrical geometry will produce resonances characteristic of that geometry. Whale's [1964] resonance at fpe 21/2 is an example. In view of all of the above, it appears difficult at this stage to predict cylindrical sheath resonances on the basis of eigenfrequencies for true wave heating already reported (Benson [1982] and references therein).…”

Section: On the Basis Of The Vacuum Dipole Theory B•r At A Distance mentioning

confidence: 99%

“…Electrons do not flow to and from the antenna but rather execute smaller orbits about an average sheath limit [Whale, 1964;Laframboise et al, 1975]. With electron current thus reduced ion ram current tends to predominate.…”

Section: Ion Datamentioning

confidence: 99%

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Sounder‐accelerated particles observed on ISIS

James¹

1983

J. Geophys. Res.

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The soft‐particle spectrometers aboard the spacecrafts ISIS I and ISIS II detect sounder‐accelerated particles, i.e., fluxes of electrons and ions energized by the 100‐μs transmitter pulse (nominal peak power: 400 W). Fluxes of up to 108 st−1 eV−1 cm−2 s−1 are observed. Typical highest electron and ion energies are several hundred electronvolts and 100–200 eV, respectively. Sounder‐accelerated electron fluxes detected on ISIS II are energized near the major electron resonant frequencies: ƒpe (plasma frequency), ƒce (gyrofrequency), 2ƒce and the oblique resonance frequency domains. Ion fluxes are present from the lowest sounder frequency (0.1 MHz) up to the greater of ƒpe and ƒce. Electrons are observed at pitch angles near 90° while ions are present at all pitch angles. The observations can be interpreted using a model of particle motion and spacecraft dc potential both induced by the intense rf field (∼100 V/m). The ion results indicate that at ƒ < ƒpe, ƒce, a negative potential of about 100 V is on the spacecraft, whereas at ƒ > ƒpe, ƒce, the potential is much smaller. ISIS I data from equatorial perigee conditions show that electrons remain energized for a few milliseconds after the end of the rf pulse.

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Section: The Electron Flux Varies As (Energymentioning

confidence: 99%

Section: On the Basis Of The Vacuum Dipole Theory B•r At A Distance mentioning

confidence: 99%

Section: On the Basis Of The Vacuum Dipole Theory B•r At A Distance mentioning

confidence: 99%

Section: Ion Datamentioning

confidence: 99%

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Sounder‐accelerated particles observed on ISIS

James¹

1983

J. Geophys. Res.

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“…region was revealed and some estimates of the influence of an ion sheath formed around sources in plasmas [13,14] and modeled by a vacuum sheath were performed. The presence of a continuous isotropic plasma region [1][2][3][4][5][6] around a source leads to an increase in the field in an outer vacuum region by 1-2 orders of magnitude compared with the case where the plasma region is absent, provided the amplitude of the feeding current at a single resonant frequency determined by the plasma-region shape remains intact.…”

Section: Figmentioning

confidence: 99%

Field of an Electric Dipole Surrounded by a Small Plasma Spheroid with a Cavity

Bichutskaya

Makarov

2005

Radiophys Quantum Electron

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We obtain and analyze a solution of the boundary-value problem for the field of an electric dipole centered in a vacuum cavity inside a small plasma spheroid. The influence of the cavity size on the field enhancement in an outer vacuum region is analyzed as a function of the curvature of the plasma-spheroid surface. The results are compared with the case of a sphere with similar cavity.This paper is the continuation of works [1][2][3][4][5][6][7][8][9][10][11][12] devoted to studying the influence of small plasma regions around a dipole source on its radiation into an outer vacuum region. Such studies are aimed at analyzing possibilities of enhancement of radiation from a small plasma region. The studies were performed for plasma regions of different shapes ranging from a circular or elliptic cylinder to a sphere and a prolate or oblate spheroid. The effect of the shape of a plasma Fig. 1.region was revealed and some estimates of the influence of an ion sheath formed around sources in plasmas [13,14] and modeled by a vacuum sheath were performed. The presence of a continuous isotropic plasma region [1-6] around a source leads to an increase in the field in an outer vacuum region by 1-2 orders of magnitude compared with the case where the plasma region is absent, provided the amplitude of the feeding current at a single resonant frequency determined by the plasma-region shape remains intact. The presence of an external magnetic field [7-10] or allowance for an ion sheath [11,12] around the source in plasma leads to splitting the resonant frequency into two frequencies and can enhance this effect.In this paper, we study the influence of the ion sheath on the far-zone field of a source surrounded by a plasma spheroid of small electrical sizes k p a 1, where k p = ω p /c, ω p is the electron plasma frequency, a is the major semiaxis of the spheroid, and c is the speed of light in free space.We consider the radiation field of an electric dipole centered in a small prolate plasma spheroid with the major and minor semiaxes a and b, respectively (Fig. 1), and the eccentricity e. The dipole is aligned with the symmetry axis of the spheroid. The ion sheath around the source is modeled by a small vacuum spheroid with the semiaxes a 1 and b 1 and the same eccentricity e. The model of an inner cavity with a sharp boundary is simplified and neglects the influence of the region with the relative dielectric permittivity ε = 0. We plan to consider this influence in future works. The distance 2d 1 between the foci of the inner spheroid is assumed to vary from the minimum value determined by the dipole length to the value almost * Yulia.Afanasyeva@paloma.spbu.ru

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Slot Admittance for Compressible Plasma Layers

Galejs

1966

Radio Science

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The admittance of a waveguide is calculated for radiation into a general two‐layer compressible plasma which is further specialized to represent a plasma sheath and also an ion sheath in the presence of a plasma half space. The antenna admittance is related by integrals to the electric fields in the waveguide aperture, which are assumed to be a sum of the principal waveguide mode and of surface wave fields which are supported in this plasma geometry. The compressibility of plasma has the largest effect on the slot admittance when the slot width is equal to an odd number of half wavelengths of surface waves, but significant changes occur only if the relative dielectric constant of the plasma is less than 0.2, and the ratio of the free‐space velocity of electromagnetic waves to the acoustic velocity is less than 300. Plasma losses and the presence of an ion sheath tend to lessen the compressibility effects.

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Ion sheath effects near antennas radiating within the ionosphere

Cited by 22 publications

References 3 publications

Sounder‐accelerated particles observed on ISIS

Sounder‐accelerated particles observed on ISIS

Field of an Electric Dipole Surrounded by a Small Plasma Spheroid with a Cavity

Slot Admittance for Compressible Plasma Layers

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