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A three-dimensional model has been developed for the plasma plumes caused by interchange instabilities in the low-latitude ionosphere to describe the structure and extent of the radio scintillation generated by turbulence around and within the plumes. With the inclusion of the processes that determine the transport of plasma parallel to the geomagnetic field lines as well as transverse to them, the model can predict the extent in latitude of the plumes and their scintillation. Diagnostics presented here include illustrations of the spectral density of the density irregularities that develop within the plumes. An extrapolation of the density irregularity spectrum down into the wavelength regime effective for radio wave scattering permits a phase screen calculation of the amplitude scintillation caused by the plumes. The scintillation produced by the model has much the same character as measurements of scintillation do in terms of the time and rate of onset of scintillation, duration, and latitudinal extent.

A three-dimensional model has been developed for the plasma plumes caused by interchange instabilities in the low-latitude ionosphere to describe the structure and extent of the radio scintillation generated by turbulence in and around the plumes (down to the scale sizes resolvable by the computer model). With the inclusion of the processes that determine the transport of plasma parallel to the geomagnetic field lines as well as transverse to them, the model can predict the extent in latitude of the plumes and their scintillation. To better reflect the day-to-day variability of the occurrence of the plumes, the model is closely coupled to a time-dependent model of the ambient ionosphere to describe the changing conditions under which the plasma instabilities that cause the turbulence must act. Diagnostics presented here will illustrate the density structures found in the models of the plumes, including maps of airglow emissions which show the effect of the density depletions within the plumes. A companion paper presents a phase-screen calculation of the amplitude scintillation caused by the plumes.

Radiation belt electrons and chorus waves are an outstanding instance of the important role cyclotron resonant wave-particle interactions play in the magnetosphere. Chorus waves are particularly complex, often occurring with large amplitude, narrowband but drifting frequency and fine structure. Nevertheless, modeling their effect on radiation belt electrons with bounce-averaged broadband quasi-linear theory seems to yield reasonable results. It is known that coherent interactions with monochromatic waves can cause particle diffusion, as well as radically different phase bunching and phase trapping behavior. Here the two formulations of diffusion, while conceptually different, are shown to give identical diffusion coefficients, in the narrowband limit of quasi-linear theory. It is further shown that suitably averaging the monochromatic diffusion coefficients over frequency and wave normal angle parameters reproduces the full broadband quasi-linear results. This may account for the rather surprising success of quasi-linear theory in modeling radiation belt electrons undergoing diffusion by chorus waves.