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Abstract

Energetic particle precipitation (EPP) connects the magnetosphere to the middle and lower atmosphere through ionization, chemical reactions, and modulation of winds. Evidence of a link to regional polar surface temperatures is provocative, where the sequence of events is still largely a black box, partly obscured by deficient EPP energy input and/or understanding of the atmospheric processes themselves.Here, we will present and discuss recent advances in respect parameterizing EPP from the radiation belt into climate models. We report on the result of the High Energy Particle Precipitation in the Atmosphere III intercomparison experiment where eight different estimates of medium energy electron (MEE) (>30 keV) ionization rates are assessed during a geomagnetic active period in April 2010. The ionization rates were all based on the Medium Energy Proton and Electron Detector (MEPED) on board the NOAA/POES and EUMETSAT/MetOp spacecraft series. However, different data handling, ionization rate calculations, and background atmospheres result in a wide range of mesospheric electron ionization rates. Moreover, we show that it is particularly challenging to model the high energy tail (>300 keV) of MEE, both in terms of the intensity as well as the timing. Finally, we shortly explore the nature of the high energy tail in the context of solar wind drivers: corotating high-speed solar wind streams (HSSs) and coronal mass ejections (CMEs) alongside their associated solar wind properties. We discuss if a stochastic approach instead of average approximations is necessary to better parameterize the daily and decadal variability of MEE.