Hybrid Alfvén resonant mode generation in the magnetosphere-ionosphere coupling system

Feedback unstable Alfvén waves involving global field-line oscillations and the ionospheric Alfvén resonator (IAR) were comprehensively studied to clarify their properties of frequency dispersion, growth rate, and eigenfunctions. It is discovered that a new mode called here the hybrid Alfvén resonan...

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Bibliographic Details
Published in:Physics of plasmas 2012-10, Vol.19 (10)
Main Authors: Hiraki, Yasutaka, Watanabe, Tomo-Hiko
Format: Article
Language:English
Subjects:
ALFVEN WAVES
CAVITY RESONATORS
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COUPLING
DISPERSIONS
EARTH MAGNETOSPHERE
EIGENFREQUENCY
EIGENFUNCTIONS
HZ RANGE
IONOSPHERE
MAGNETIC FIELDS
OSCILLATIONS
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Summary:Feedback unstable Alfvén waves involving global field-line oscillations and the ionospheric Alfvén resonator (IAR) were comprehensively studied to clarify their properties of frequency dispersion, growth rate, and eigenfunctions. It is discovered that a new mode called here the hybrid Alfvén resonant (HAR) mode can be destabilized in the magnetosphere-ionosphere coupling system with a realistic Alfvén velocity profile. The HAR mode found in a high frequency range over 0.3 Hz is caused by coupling of IAR modes with strong dispersion and magnetospheric cavity resonances. The harmonic relation of HAR eigenfrequencies is characterized by a constant frequency shift from those of IAR modes. The three modes are robustly found even if effects of two-fluid process and ionospheric collision are taken into account and thus are anticipated to be detected by magnetic field observations in a frequency range of 0.3–1 Hz in auroral and polar-cap regions.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.4759016