Abstract Electric field spectrum measurements from the plasma wave instrument on Dynamics Explorer 1 are used to study the local electron density at high altitudes in the polar cap and nightside auroral zone. The electron density is derived from the upper cutoff of the whistler-mode auroral hiss emissions at the electron plasma frequency. In the nightside auroral zone, sharply defined regions of low electron densities are commonly found to occur. Electron densities in these regions are strongly depleted in relation to the adjacent plasmaspheric and polar densities, forming a low density cavity at 70° ± 5° invariant latitude. A comparison of these density depletions with simultaneous particle measurements indicates a correspondence between low auroral plasma densities, upflowing ion distributions and an energetic precipitating electron population. These correlations show that density depletions in the nightside auroral zone are directly associated with auroral acceleration processes. Inside the polar cap, density values are found to vary inversely with increasing radial distance, falling by more than two orders of magnitude over an altitude range of 1.75–4.66 RE. The observed variation indicates a power law distribution of densities, consistent with a steady-state radial outflow of ionospheric plasma along polar magnetic field lines.


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    Title :

    Electron density distributions in the high-latitude magnetosphere


    Contributors:

    Published in:

    Publication date :

    1989-01-01


    Size :

    10 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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