Electron Inertial Effects on Linearly Polarized Electromagnetic Ion Cyclotron Waves at Earth's Magnetosphere

Document Type

Article

Publication Date

4-1-2019

Keywords

Electromagnetic ion cyclotron waves, Ion-ion hybrid resonance, Electron inertial waves

Abstract

We discuss a role of the electron inertial effect on linearly polarized electromagnetic ion cyclotron (EMIC) waves at Earth. The linearly polarized EMIC waves have been previously suggested to be generated via mode conversion from the fast compressional wave at the ion‐ion hybrid (IIH) resonance. When the electron inertial effects are neglected, the wave normal angle of the mode‐converted IIH waves is 90° because the wave vector perpendicular to the magnetic field becomes infinite at the IIH resonance. When the electron inertial effect is considered, the mode‐converted IIH waves can propagate across the magnetic field lines, and the wavelength perpendicular to the magnetic field approaches the electron inertial length scale near the Buchsbaum resonance. These waves are referred to as electron inertial waves. Due to the electron inertial effect, the perpendicular wave number to the ambient magnetic field near the IIH resonance remains finite, and the wave normal angle is less than 90°. The wave normal angle where the maximum absorption occurs in a dipole magnetic field is 30–80°, which is consistent with the observed values near the magnetic equator. Therefore, the numerical results suggest that the linearly polarized EMIC wave generated via mode conversion near the IIH resonance can be detected in between the Buchsbaum and the IIH resonance frequencies, and these waves can have normal angle less than 90°.

Journal Title

Journal of Geophysical Research: Space Physics

Volume

124

Issue

4

First Page

2643

Last Page

2655

DOI

https://doi.org/10.1029/2019JA026532

First Department

Engineering

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