Auroral-E Electron Density Profiles to be Derived From SESS Particle Data

Studies are being conducted prior to the design and development of an algorithm for deriving auroral-E electron density profiles (EDPs) from LEPS (Low Energy Particle Sensor) auroral particle data recorded on board future NPOESS satellites. LEPS will measure spectra of auroral electrons and protons at several pitch angles over approximately 90° starting with near-vertical-viewing (not necessarily near-field-aligned-viewing). Its energy ranges (for electrons and protons) will be similar to those of the SSJ4 and SSJ5 (30 eV to 30 keV) sensors on DMSP and the TED sensor on POES with an extension to 50 keV. There will be times during disturbed periods when significant energy flux can be expected to reside above the LEPS high-energy cutoff based on SSJ4, SSJ5, and TED measurements to date. In such situations, it will be advisable to include MEPS (Medium Energy Particle Sensor) data rather than attempt an energy extrapolation of LEPS data. Our basic approach to the overall algorithm will be discussed including specification of altitude profiles of ion production rates for both electron and proton spectra and the subsequent specification of the EDP itself. Selected results from studies will also be presented such as errors arising from the choice of technique for specifying ion production rates from the measured spectra (in a statistical sense based on the use of extensive SSJ5 spectra) and the impact of field-aligned precipitation on the accuracy of the measured incoming hemispherical energy flux (being extrapolated to the field-aligned direction) and on derived EDPs. FAST data and extensive particle transport runs support our studies into anisotropy effects.