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  1. Abstract

    We present a global survey of energetic electron precipitation from the equatorial magnetosphere due to hiss waves in the plasmasphere and plumes. Using Van Allen Probes measurements, we calculate the pitch angle diffusion coefficients at the bounce loss cone, and evaluate the energy spectrum of precipitating electron flux. Our ∼6.5‐year survey shows that, during disturbed times, hiss inside the plasmasphere primarily causes the electron precipitation atL > 4 over 8 h < MLT < 18 h, and hiss waves in plumes cause the precipitation atL > 5 over 8 h < MLT < 14 h andL > 4 over 14 h < MLT < 20 h. The precipitating energy flux increases with increasing geomagnetic activity, and is typically higher in the plasmaspheric plume than the plasmasphere. The characteristic energy of precipitation increases from ∼20 keV atL = 6–∼100 keV atL = 3, potentially causing the loss of electrons at several hundred keV.

     
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  2. ISRs measure backscattered power that is proportional to electron density in the ionosphere (e.g., Dougherty and Farley, 1961; Evans, 1969). To quantify electron density enhancements, a forward model that characterizes the physics of particle precipitation must be developed. Transport models describe the physics of how particle precipitation generates ionization enhancements, while chemistry models describe how ionization modifies the background electron density. In this section, we briefly review particle transport processes and chemistry and provide a brief review of techniques used to estimate particle differential number flux from enhanced electron density measurements. 
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