Estimation of Heavy Ion Densities From Linearly Polarized EMIC Waves At Earth
Authors: Eun-Hwa Kim, Jay R. Johnson and Dong-Hun Lee
Abstract:
Linearly polarized EMIC waves are expected to concentrate
at the location where their wave frequency satisfies the
ion-ion hybrid (IIH) resonance condition as the result of a
mode conversion process. In this letter, we evaluate absorption
coefficients at the IIH resonance in the Earth geosynchronous
orbit for variable concentrations of helium and azimuthal
and field-aligned wave numbers in dipole magnetic
field. Although wave absorption occurs for a wide range of
heavy ion concentration, it only occurs for a limited range of
azimuthal and field-aligned wave numbers such that the IIH
resonance frequency is close to, but not exactly the same
as the crossover frequency. Our results suggest that, at
L = 6.6, linearly polarized EMIC waves can be generated
via mode conversion from the compressional waves near the
crossover frequency. Consequently, the heavy ion concentration
ratio can be estimated from observations of externally
generated EMIC waves that have polarization.
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Submitted to: Geophysical Research Letter, (February 2014)
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