An experimental study of the role of hiss in the generation of chorus in the outer magnetosphere, as based on spectral analyses and direction finding measurements onboard GEOS 1

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概要

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• The satellite and ground VLF data have indicated that chorus is often accompanied by a background hiss, and the purpose of this paper is to investigate the association between hiss and chorus and to present detailed experimental findings on the cause and effect relationship between hiss and chorus. The present study is based on detailed spectral analyses and direction finding measurements for VLF emission events with the simultaneous occurrence of hiss and chorus observed by GEOS-1 satellite in the outer magnetosphere. Two different events are analyzed : one is the equatorial (geomag. lat.=6.8°-8.5°) event, and the other the off-equatorial (24.2°-23.6°) event. The following important experimental findings have emerged from the present study : (1) Each chorus element originates from the hiss band and is asymptotic to the hiss band. (2) The intensity and occurrence of chorus emissions are closely correlated with the intensity of the underlying hiss band, such that when the intensity of the hiss band exceeds a threshold value of some mγ/√<Hz>, the excitation of chorus emission is enhanced. (3) Some parts of hiss band exhibit some structures or wavelets (i.e. monochromatic wave components with duration of more than 100ms), although hiss has been considered to be incoherent and turbulent. Furthermore, on some occasions, we can notice an existence of wavelets at the foot of chorus elements. (4) The direction finding results have newly indicated similar values for the azimuthal direction φ for both phenomena, suggesting that both hiss and chorus come from the same source region. These experimental facts suggest that a wavelet existing in the hiss band may generate a chorus emission through coherent wave-particle interaction in the outer magnetosphere as in the case of active VLF wave injection experiments.

• 国立極地研究所の論文

著者

• Parrot Michel

  Laboratoire De Physique Et Chimie De L'environnement

• HAYAKAWA Masashi

  University of Electro-Communications

• LEFEUVRE Francois

  Laboratoire de Physique et Chimie de l'Environnement

• Hattori Katsumi

  Solar-Terrestrial Environmental Laboratory, Nagoya University

• Hayakawa Masashi

  Solar-Terrestrial Environmental Laboratory, Nagoya University

• Lagoutte Dominique

  Laboratoire de Physique et Chimie de l'Environnement

• Hattori Katsumi

  Solar-terrestrial Environmental Laboratory Nagoya University

• Hayakawa M

  Univ. Electro‐communications Chofu‐shi Jpn

• Lefeuvre F.

  Laboratoire De Physique Et Chimie De L'environnement

• Lagoutte Dominique

  Laboratoire De Physique Et Chimie De L'environnement

• Hayakawa Masashi

  Solar-terrestial Environment Laboratory Nagoya University

関連論文

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• An experimental study of the role of hiss in the generation of chorus in the outer magnetosphere, as based on spectral analyses and direction finding measurements onboard GEOS 1
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• On the Estimation of Wave Energy Distribution of Magnetospheric VLF Waves at the Ionospheric Base with Ground-Based Multiple Electromagnetic Field Components
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