Equatorially generated ULF waves as a source for the turbulence associated with ion conics

Low frequency turbulence present on closed field lines the central plasma sheet has been used to explain ion heating and conic formulation with remarkable success. However, the source for 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 waves both above and below the proton gyrofrequency. 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, and as a result, downcoming right-hand circularly polarized waves, which acquire a left-hand circularly polarized component at the crossover frequency, may tunnel through stop zone to altitudes where they resonate with the ions and thus contribute to the observed ion heating. Keywords: Equatorial turbulence, Electromagnetic waves, Mode conversion, Ion conics, Reprints. (jhd)

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