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Amplification of electromagnetic ion cyclotron waves along a wave path in the Earth's multicomponent magnetosphere
Author(s) -
Hu Y. D.,
Fraser B. J.,
Olson J. V.
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i008p01053
Subject(s) - magnetosphere , physics , equator , geophysics , ring current , earth's magnetic field , cyclotron , field line , electromagnetic radiation , magnetic field , computational physics , latitude , optics , astronomy , quantum mechanics
In this report, we consider the amplification of electromagnetic ion cyclotron waves along a geomagnetic field line in the multicomponent magnetosphere, assuming that the waves propagate parallel to the background magnetic field. We find it is possible for the ring‐current protons (energy ∼10–100 keV), which supply the free energy to stimulate the waves, to resonate with the waves not only in the equatorial region but also off the equator. An instability, caused by a thermal anisotropy, may occur in separated regions on and/or off the equator. The positions of the source regions along the wave path depend on the concentration of cold heavy ion species. The significant off‐equator source regions may be located at geomagnetic latitudes where the waves, with frequencies greater than the He + gyrofrequency on the equator, are in a local He + pass band.