Computer Science – Performance
Scientific paper
Jul 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011jgra..11607303c&link_type=abstract
Journal of Geophysical Research, Volume 116, Issue A7, CiteID A07303
Computer Science
Performance
Atmospheric Composition And Structure: Airglow And Aurora, Atmospheric Composition And Structure: General Or Miscellaneous, Ionosphere: Particle Precipitation, Ionosphere: General Or Miscellaneous
Scientific paper
A significantly higher N2 Lyman-Birge-Hopfield (LBH) emission efficiency for auroral proton precipitation compared to model calculations was reported by Knight et al. (2008) based on a statistical study utilizing coincident far ultraviolet and particle data from the sensors Special Sensor Ultraviolet Spectrographic Imager (SSUSI) and Special Sensor J/5 (SSJ/5) on board the DMSP satellite F16. Here, the quantity of interest from that study is the median ratio of LBH column emission rates (CERs) from SSUSI and derived from SSJ/5 spectra using monoenergetic emission yields. The median ratio was found to be 2.83 for proton aurora, suggesting the need for significant increases in currently used LBH proton/H-atom impact cross sections. A key step in their analysis was extrapolation of SSJ/5 spectra above 30 keV. Limited testing of this algorithm using NOAA Polar Orbiting Environmental Satellites Total Energy Detector and Medium Energy Proton and Electron Detector (TM) data found no significant bias. This work reports on a more detailed investigation of the algorithm's performance, also using TM data, and has uncovered a bias that reduces the median column emission rates (CER) ratio to 1.75. Within expected uncertainties, including calibration, this still calls for cross section increases but to a lesser extent. The discovered bias becomes apparent with CER thresholding that was overlooked during testing by Knight et al. (2008). Thresholding at 400 Rayleighs (R) is necessary since Knight et al. excluded CERs < 400 R in deriving their median ratio. We show that the algorithm's performance degrades with increasing energy flux of the precipitation. A method is reported for eliminating most of the bias which utilizes auroral Ly α, whose emission strength is closely coupled to spectral hardness.
Correira J.
Evans Steven J.
Hecht James H.
Knight H. K.
Strickland Douglas J.
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