Atmospheric Effects of >30‐keV Energetic Electron Precipitation in the Southern Hemisphere Winter During 2003

• Published in: Journal of geophysical research. Space physics 2019-10, Vol.124 (10), p.8138-8153
• Main Authors: Pettit, J. M., Randall, C. E., Peck, E. D., Marsh, D. R., Kamp, M., Fang, X., Harvey, V. L., Rodger, C. J., Funke, B.
• Format: Article
• Language: English
• Subjects: Astronomical instruments; Atmosphere; Atmospheric chemistry; Atmospheric effects; Atmospheric models; Auroral electrons; Climate models; Computer simulation; Datasets; Electron density; Electron flux; Electron precipitation; Electrons; Energy; Estimates; Geomagnetic activity; geomagnetic storms; Geomagnetism; Global climate; Global climate models; Hydrogen; mesosphere; middle atmosphere; Nitrogen oxides; NOx production; Organic chemistry; Ozone; Photochemicals; Pitch (inclination); Precipitation; Protons; Satellite instruments; Satellite observation; Satellite-borne instruments; Satellites; Simulation; Southern Hemisphere; Telescopes; WACCM
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2019JA026868

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. Plain Language Summary The study presented here investigates the effects from energetic electron precipitation (EEP) in the southern hemisphere winter of 2003. Electron precipitation is common during periods of enhanced geomagnetic activity and can create reactive nitrogen oxides and hydrogen oxides that can destroy ozone. Most global climate models currently do not include precipitating electrons with energies greater than 30 keV. To test whether this deficiency is important, this investigation compares observations with model simulations that included electrons with energies greater than 30 keV, as observed by the Medium Energy Proton and Electron Detector (MEPED) satellite instruments. In addition, one of the EEP data sets used in the simulations included data from just one of the telescopes on the MEPED instruments, whereas the other included data from b