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Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron wavesElectromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Thorne, Richard M. (University of California, Los Angeles, CA United States)
Horne, Richard B. (Natural Environment Research Council, Cambridge, England United Kingdom)
Date Acquired
August 16, 2013
Publication Date
September 1, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: A9
ISSN: 0148-0227
Subject Category
Funding Number(s)
Distribution Limits