Theoretical analysis of Poynting flux and polarization for ELF-VLF electromagnetic waves in the Earth's magnetosphere

We discuss properties of extremely low‐frequency (ELF) and very low‐frequency (VLF) electromagnetic waves in the Earth's magnetosphere. General expressions for wave magnetic field polarization and for the angle θP between the direction of the Poynting flux vector and the ambient magnetic field...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2013-12, Vol.118 (12), p.7695-7702
Main Authors: Verkhoglyadova, O. P., Tsurutani, B. T., Lakhina, G. S.
Format: Article
Language:English
Subjects:
Astronomy
chorus
Earth science
Earth, ocean, space
Electromagnetic radiation
energy flux
Exact sciences and technology
External geophysics
Fluctuations
Geophysics
Interplanetary space
Magnetic fields
Physics of the ionosphere
Physics of the magnetosphere
plasmaspheric hiss
Polarization
Solar system
Theoretical analysis
wave polarization
Wave propagation
Wavelengths
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Summary:We discuss properties of extremely low‐frequency (ELF) and very low‐frequency (VLF) electromagnetic waves in the Earth's magnetosphere. General expressions for wave magnetic field polarization and for the angle θP between the direction of the Poynting flux vector and the ambient magnetic field are derived for low‐amplitude (linear) waves taking into account first‐order finite gyroradius effects. The wave magnetic field is always in a plane perpendicular to the direction of the wave propagation, and the polarization depends on wave frequency (or wavelength), dispersion, and plasma parameters. In a warm plasma, the Poynting flux is not aligned with the group velocity and generally deviates from the wave propagation direction, except for parallel propagation. Numerical estimates for θP and wave polarization are made for plasmaspheric hiss (at L=2, 4, and 6) for typical plasma parameters and for the case of elevated electron temperature (5 keV). The plasmaspheric hiss wave magnetic field is right‐hand circularly polarized, except for highly oblique hiss waves which are elliptically polarized. We note a possible transition to the magnetosonic wave regime at short wavelengths. The maximum Poynting flux angle is ∼20°. Estimates for daytime outer zone chorus (L=6) show two regions of oblique Poynting flux corresponding to a low‐frequency band (ω
ISSN:2169-9380
2169-9402
DOI:10.1002/2013JA019371