A correction method to remove proton contamination from the electron channels of the Polar-orbiting Operational Environmental Satellites Medium Energy Proton/Electron Detector (MEPED) is described. Proton contamination estimates are based on measurements in five of the MEPED proton spectral channels. A constrained inversion of the MEPED proton channel response function matrix is used to calculate proton differential flux spectra. In this inversion, the proton energy distribution is described by a weighted combination of exponential, power law, and Maxwellian distributions. Proton contamination in the MEPED electron spectral channels is derived by applying the electron channel proton sensitivities to the proton fluxes from the best fit proton spectra. Once the electron channel measurements are corrected for proton contamination, an inversion of the electron channel response function matrix is used to calculate electron differential flux spectra. A side benefit of the method is that it yields an estimate for the integrated electron flux in the energy range from 300 keV to 2.5 MeV with a center energy at~800 keV. The final product is a differential spectrum of electron flux covering the energy range from about 10 keV to 2.5 MeV that is devoid of proton contamination except during large solar proton events. Comparisons of corrected MEPED differential fluxes to the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions Instrument for Detecting Particles show that MEPED fluxes are greater than what is expected from altitude-induced particle population changes; this is attributed at least partially to measurement differences in pitch angle range.

[1] We investigate the influence of major sudden stratospheric warming (SSW) and elevated stratopause (ES) events in the Northern Hemisphere winter on the transport of NO x produced by energetic particle precipitation (EPP) from the mesosphere-lower thermosphere to the stratosphere using the Whole Atmosphere Community Climate Model (WACCM). Increases in NO x following a major SSW and/or ES event are in excess of 100% compared to winters when no major SSW or ES event occurred. The increase in NO x is attributed to an increase in the descending branch of the residual circulation (w * ) following the event. The timing of the event strongly affects the amount of NO x that descends to the stratosphere: the earlier the event occurs, the more NO x descends to the stratosphere. We also quantify the amount of NO x produced by EPP descending to the stratosphere in each winter and find that the largest increases in NO x are in years that have a major SSW followed by an ES event early in the season (December or early January). The strength of w * following an event shows a very strong seasonal dependence and explains why the timing of the event affects the transport of NO x .Citation: Holt, L. A., C. E. Randall, E. D. Peck, D. R. Marsh, A. K. Smith, and V. L. Harvey (2013), The influence of major sudden stratospheric warming and elevated stratopause events on the effects of energetic particle precipitation in WACCM,

The atmospheric effects of precipitating electrons are not fully understood, and uncertainties are large for electrons with energies greater than ~30 keV. These electrons are underrepresented in modeling studies today, primarily because valid measurements of their precipitating spectral energy fluxes are lacking. This paper compares simulations from the Whole Atmosphere Community Climate Model (WACCM) that incorporated two different estimates of precipitating electron fluxes for electrons with energies greater than 30 keV. The estimates are both based on data from the Polar Orbiting Environmental Satellite Medium Energy Proton and Electron Detector (MEPED) instruments but differ in several significant ways. Most importantly, only one of the estimates includes both the 0° and 90° telescopes from the MEPED instrument. Comparisons are presented between the WACCM results and satellite observations poleward of 30°S during the austral winter of 2003, a period of significant energetic electron precipitation. Both of the model simulations forced with precipitating electrons with energies >30 keV match the observed descent of reactive odd nitrogen better than a baseline simulation that included auroral electrons, but no higher energy electrons. However, the simulation that included both telescopes shows substantially better agreement with observations, particularly at midlatitudes. The results indicate that including energies >30 keV and the full range of pitch angles to calculate precipitating electron fluxes is necessary for improving simulations of the atmospheric effects of energetic electron precipitation.