HAO Colloquium - Hilde Nesse Tyssøy, University of Bergen

Energetic Electron Precipitation into the Earth's Atmosphere 

Energetic Particle Precipitation (EPP), ionizing the polar thermosphere and mesosphere, haveong been known to initiate a series of chemical reactions increasing the production of NOx and HOx gasses. HOx and NOx gasses will destroy ozone in catalytic reactions, and it is speculated that the subsequent change in temperature might alter stratospheric winds and wave propagation. Quantitative measurements of Energetic Electron Precipitation (EEP) are still, however, an outstanding question and a key to resolve the total EPP impact on the atmosphere, as well as the varying nature of the radiation belts.

The Medium Energy Proton and Electron Detector (MEPED) instrument on board the NOAA/Polar Orbiting Environmental Satellites (POES) has two sets of electron telescopes pointing ~0° and ~90° to the local vertical. We estimate the Bounce Loss Cone (BLC) fluxes based on both detectors combined with theory of pitch-angle diffusion due to wave-particle interaction. The BLC fluxes are compared to the current parameterization recommended for the Coupled Model Intercomparison Project. We find that the EEP fluxes during weak, but long-lasting EEP events associated with high speed solar wind streams are strongly underestimated. We show that the level of pitch angle anisotropy increases with increased flux levels in the recovery periods of the storms. Potential acceleration and pitch angle scattering sources are discussed, as well as the associated implications for quantifying EEP into the atmosphere.

Date and time: 
Wednesday, November 6, 2019 - 2:00pm to 3:00pm