Whistler wave ducting caused by antenna actions

Sugai, Hideo; Maruyama, Masahiko; Sato, Masanori; Takeda, Susumu

doi:10.1063/1.862278

Cited by 68 publications

(29 citation statements)

References 15 publications

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“…Stenzel's work in slowly-varying plasma was extended by Sugai and coworkers [Sugai et al, 1978a[Sugai et al, , 1978b[Sugai et al, , 1979[Sugai et al, , 1980. From the early 1980's laboratory research on whistler waves has continued but in directions that are not relevant to this discussion.…”

Section: Introductionmentioning

confidence: 97%

“…As well, he goes on to measure the phase and amplitude distribution of the antenna radiation pattern in both uniform and slowly-varying plasmas. In the nonuniform case, refraction is observed as well as ducting in a density trough.Stenzel's work in slowly-varying plasma was extended by Sugai and coworkers [Sugai et al, 1978a[Sugai et al, , 1978b[Sugai et al, , 1979[Sugai et al, , 1980. From the early 1980's laboratory research on whistler waves has continued but in directions that are not relevant to this discussion.…”

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confidence: 97%

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A whistler wave interaction with a density striation: a laboratory investigation of an auroral process

Gekelman

Maggs

Bamber

et al. 1996

IEEE Trans. Plasma Sci.

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Whistler waves are launched toward a field-aligned density striation in a laboratory plasma. Characteristic scale length and frequency ratios are scaled to closely reproduce situations found in the auroral ionosphere. Detailed measurements show that at the striation edge nearest the wave-launching antenna, besides a reflected and a transmitted whistler wave, lower hybrid waves are also stimulated on both sides of the striation boundary in a manner consistent with the linear mode-conversion model. We find that the energy density of the mode-converted lower hybrid waves is typically 10% of the incident whistler wave energy density, reaching a maximum of 30% in one region. Lower hybrid waves are confined to within 2-3 perpendicular wavelengths in the interaction zone. Our results show that the interaction of electromagnetic whistler mode waves with density striations can cause significant amounts of energy to be deposited in the largely electrostatic lower hybrid mode and that it may, therefore, be a significant generation mechanism for these waves in certain regions of the ionosphere. 2 IntroductionThe investigation of the behavior of electromagnetic whistler waves in the vicinity of a field-aligned density striation is motivated by a number of observations made in the near-earth environment. First, these waves are commonly found in almost all parts of the magnetosphere and ionosphere [Helliwell, 1965;Walker, 1976;Shawhan, 1979;Al'pert, 1980Al'pert, , 1983and Carpenter, 1983]. Second, at altitudes below approximately 5000 km, the high latitude ionospheric plasma is found to contain short scale-length, field-aligned irregularities or striations [Herman, 1966;Dyson, 1969;Clark and Raitt, 1976;Kelley and Mozer, 1972;Fejer and Kelley, 1980] at all accessible altitudes and all local times. The striations are almost always of lower density than the background and the density amplitude distribution peaks between 10% and 30% of the background level [Dyson, 1969]. It is generally believed that the size of the striation parallel to the background magnetic field is very large compared to its extent across the field so that the shape is either cylinder-like or sheet-like. The cross-field dimension ranges from as small as 10 m to hundreds of km.Although striations are basically a high-latitude phenomenon, with most observations being made at L ≥ 4 (invariant latitude |Λ| ≥ 60°), there is also a small region where striations exist near the magnetic equator, |Λ| ≤ 20° [Kelley and Mozer, 1972]. Clearly, whistler waves propagating in these regions must frequently encounter density striations. The electromagnetic whistler wavelength in the topside ionosphere is on the order of 1 km. Measurements with very high spatial resolution made in the ionosphere below 1000 km, on a series of rocket flights , directly show the existence of the small-scale density striations which are typically 100 m across (minimum 10 m) with an average spacing of ~1 km. It 3 is the interaction of whistler waves with this type of short perpendicular scale leng...

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Section: Introductionmentioning

confidence: 97%

mentioning

confidence: 97%

A whistler wave interaction with a density striation: a laboratory investigation of an auroral process

Gekelman

Maggs

Bamber

et al. 1996

IEEE Trans. Plasma Sci.

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“…Density perturbations by ponderomotive force or thermal pressure can produce a density trough which guide whistlers [99][100][101]. Focusing resonance cones produces density holes, fast ions, and low-frequency turbulence [82].…”

Section: Nonlinear Whistlersmentioning

confidence: 99%

Whistler waves with angular momentum in space and laboratory plasmas and their counterparts in free space

Stenzel

2016

Advances in Physics: X

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Electromagnetic waves with helical phase surfaces arise in different fields of physics such as space plasmas, laboratory plasmas, solid-state physics, atomic, molecular and optical sciences. Their common features are the wave orbital angular momentum associated with the circular wave propagation around the axis of wave propagation. In plasmas these waves are called helicons. When particles or waves change the field momentum they experience a pressure and a torque which can lead to useful applications. In plasmas electrons can damp or excite rotating whistlers, depending on the electron distribution function in velocity space. A magnetized plasma is an anisotropic medium in which electromagnetic waves propagate differently than in space. Phase and group velocities are different such that wave focusing and wave reflections are different from those in free space. Electrons experience Doppler shifts and cyclotron resonance which creates wave damping and growth. All media exhibit nonlinear effects which do not occur in free space. Common and different features of vortex waves in different fields will be reviewed. However, a comprehensive review of this vast field is not possible and further readings are referred to the cited literature. ARTICLE HISTORY

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“…A number of important features of whistler wave radiation from monochromatic sources in the presence of density ducts have been documented in Refs. [10][11][12][13][14][15][16][17][18][19][20]. In particular, it has been demonstrated that under certain conditions, the presence of a duct can significantly improve the antenna coupling into whistler-mode waves.…”

Section: Introductionmentioning

confidence: 99%

“…A great deal of attention has particularly been devoted to whistler wave excitation in laboratory and space plasmas containing magnetic-fieldaligned density irregularities. [10][11][12][13][14][15][16][17][18][19][20][21][22] Such irregularities, commonly known as density ducts, can exist in the Earth's magnetosphere, in which they ensure guidance of whistler-mode waves naturally occurring under space plasma conditions. 25 Of no less interest are artificial density ducts that can arise due to various nonlinear effects near electromagnetic sources in laboratory and space plasmas.…”

Section: Introductionmentioning

confidence: 99%

Whistler wave radiation from a pulsed loop antenna located in a cylindrical duct with enhanced plasma density

Kudrin¹,

Shkokova²,

Ferencz

et al. 2014

Physics of Plasmas

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Pulsed radiation from a loop antenna located in a cylindrical duct with enhanced plasma density is studied. The radiated energy and its distribution over the spatial and frequency spectra of the excited waves are derived and analyzed as functions of the antenna and duct parameters. Numerical results referring to the case where the frequency spectrum of the antenna current is concentrated in the whistler range are reported. It is shown that under ionospheric conditions, the presence of an artificial duct with enhanced density can lead to a significant increase in the energy radiated from a pulsed loop antenna compared with the case where the same source is immersed in the surrounding uniform magnetoplasma. The results obtained can be useful in planning active ionospheric experiments with pulsed electromagnetic sources operated in the presence of artificial field-aligned plasma density irregularities that are capable of guiding whistler waves.

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Whistler wave ducting caused by antenna actions

Cited by 68 publications

References 15 publications

A whistler wave interaction with a density striation: a laboratory investigation of an auroral process

A whistler wave interaction with a density striation: a laboratory investigation of an auroral process

Whistler waves with angular momentum in space and laboratory plasmas and their counterparts in free space

Whistler wave radiation from a pulsed loop antenna located in a cylindrical duct with enhanced plasma density

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