Mesospheric Hydroxyl Response to Electron Precipitation From the Radiation Belts

Details Mesospheric Hydroxyl Response to Electron Precipitation From the Radiation Belts Mesospheric Hydroxyl Response to Electron Precipitation From the Radiation Belts

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa23b..05v&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SA23B-05

Physics

[0340] Atmospheric Composition And Structure / Middle Atmosphere: Composition And Chemistry, [2427] Ionosphere / Ionosphere/Atmosphere Interactions, [2716] Magnetospheric Physics / Energetic Particles: Precipitating, [2774] Magnetospheric Physics / Radiation Belts

Scientific paper

High-energy particle precipitation affects the neutral chemistry of the middle atmosphere. For example, ozone-destroying catalytic reactions take place after particle impact ionization and ion chemistry produce excess amounts of odd hydrogen ({HOx} = {H} + {OH} + {HO2}) and odd nitrogen ({NOx} = N + NO + {NO2}). In the upper stratosphere and mesosphere, substantial changes in ozone have been observed by satellites especially after large solar proton events. Changes in stratospheric ozone could cause changes in the general circulation and climate, but the connecting mechanisms are not yet understood. Unlike in the case of solar protons, electrons are first captured and stored by Earth's magnetosphere, e.g. the radiation belts, from where they are eventually lost into the atmosphere especially during magnetic storms which can accelerate the electrons to high energies. The significance of energetic electron precipitation (EEP) to the mesospheric chemistry is poorly known because continuous flux measurements are particularly hard to make due to the relatively small size of the bounce loss cone at satellite altitudes. In this study, using observations from the Medium Energy Proton and Electron Detector (MEPED) onboard the Polar Orbiting Environmental Satellite (POES) and the Microwave Limb Sounder (MLS) onboard the Aura satellite, we demonstrate that there is a strong link between 100 - 300 keV loss cone electron count rates observed in the outer radiation belt and night-time {OH} concentrations of the middle mesosphere at 71 - 78 km altitude. We consider daily mean data from two months, March 2005 and April 2006, which were selected because of 1) relatively high count rates of radiation belt electrons observed 2) the absence of solar proton events that could dominate ionization in the mesosphere and mask the EEP effects. The results show that at 55 - 65° magnetic latitude (equivalent to McIlwain L shells 3.0 - 5.6) increases in electron count rate by two orders of magnitude are accompanied by increases in {OH} concentration of 100%. There is a strong and significant correlation between MEPED and MLS data such that 56 - 87% of the {OH} variation can be explained by changes in EEP. This is clear evidence of direct {HOx} response to EEP, and an indication that EEP can drive significant in-situ changes in neutral atmospheric chemistry.

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