" Pathways to Thermospheric Heating via Cusp Electron Precipitation " Binzheng Zhang, Research Scientist, Thayer School of Engineering
ABSTRACT: The effects of precipitating soft electrons on the thermospheric mass density in the dayside cusp region are investigated using the coupled magnetosphere- ionosphere thermosphere model (CMIT). Simulation results show that while soft electrons have relatively minor effects on the interaction between the magnetosphere and ionosphere, they can significantly modify the mass density of the thermosphere in the dayside cusp region. Event simulations show that the CMIT model is capable of reproducing the mass density enhancement measured by the CHAMP and GRACE satellite at 400 km. The efficiencies of the direct and indirect thermospheric heating processes associated with precipitating soft electrons are investigated using ideal and event-based CMIT simulations. Preliminary results show that direct heating from soft electrons to thermospheric neutrals only has little effect on the neutral temperature and density, and indirect heating is the dominant process in the thermospheric neutral density enhancement. In the indirect heating process, precipitating soft electrons enhance the altitude profile of F-region Pedersen conductivity, which modifies the altitude distribution of the Joule heating in the cusp region and causes the enhancement of neutral temperature and density more efficiently than the direct heating process.
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