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Large-Scale Plasma Density Fluctuations Measured with the HILAT Satellite at 830 Km Altitude.
REGIS COLL RESEARCH CENTER WESTON MA
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Measurements from the plasma monitor on the HILAT satellite have been used to map the distribution of large scale fluctuations in the density of plasma at high latitudes. Digital filtering has been used to separate the original data into three frequency bands. The output from the middle band pass filter has been used to count and map the distribution of large-scale plasma density enhancements. Maps of blob distribution are drawn as a function of magnetic local time and invariant latitude, for both low and high magnetic activity. To serve as a point of reference the same filtering and counting techniques are applied to measurements of the ion drift velocity to show the distribution of electric field fluctuations. Additionally, from the power levels measured at two different frequencies, the average spectral slopes of both the plasma density and electric field have been mapped. The results show that large scale plasma enhancements are created in the auroral zone and are transported away from the production regions by convection. Movement of blobs from the cusp to polar cap is very prominent. The spectral slope of the plasma density is significantly increased in the night side, from 23 to 2 hour magnetic local time. The intermediate scale plasma irregularities appear to be dissipated in this region. Enhanced radio scintillations had been measured with the HILAT radio beacon in the same locations.
APPROVED FOR PUBLIC RELEASE