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Equatorially generated ULF waves as a source for the turbulence associated with ion conics
Author(s) -
Johnson Jay R.,
Chang Tom,
Crew G. B.,
André Mats
Publication year - 1989
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/gl016i012p01469
Subject(s) - physics , cyclotron , ion , computational physics , magnetic field , turbulence , atomic physics , wave turbulence , anisotropy , harmonics , wave propagation , optics , mechanics , quantum mechanics , voltage
Low frequency turbulence present on closed field lines in the central plasma sheet has been used to explain ion heating and conic formation with remarkable success. However, the source of the turbulence has yet to be established, and there are no obvious local sources which could power such a broadband spectrum. Alternatively, observations reveal that ion distributions in the equatorial region are often anisotropic, and such distributions excite both ion cyclotron waves below the proton gyrofrequency and waves near the harmonics of the hydrogen cyclotron frequency. As these waves propagate to lower altitudes where the magnetic field is stronger, their left‐hand circularly polarized component resonates with heavy ions. The presence of a parallel gradient in the magnetic field complicates the details of wave propagation so that downcoming right‐hand circularly polarized waves, which acquire a left‐hand circularly polarized component at the crossover frequency, may tunnel through a “stop zone” to altitudes where they contribute to the observed ion heating.