An improved model of energetic electron precipitation providing a long-term ionization dataset for CMIP7

Medium-energy electron precipitation (MEE; energies between about 30 keV and 1 MeV) in the upper atmosphere is a source of a chain of chemical reactions which ultimately affect temperature and circulation in the lower atmosphere, and is therefore a significant component to be taken into account in chemistry climate models. In this paper, a new electron precipitation model is presented, offering several upgrades and improvements over earlier versions. The model was developed using the electron flux observations of the Polar-orbiting Operational Environmental Satellites (POES) from 1998–2023. The electron content of the bounce loss cone was derived from both the 0-degree and 90-degree channels of the latest generation of the instrument onboard POES in combination with a theoretical model of pitch-angle diffusion. The data were corrected and calibrated for proton contamination and instrument sensitivity. The electron fluxes are modeled separately in three separate energy ranges (30–100, 100–300 and 300–1000 keV), with a 1-day time resolution, as functions of corrected geomagnetic latitude and of time series of the geomagnetic index Ap. In the model, the Ap index is integrated over a convolution function in time, to account for a latitude- and energy-dependent delay in response to geomagnetic disturbances. The energy spectrum between 30 and 1000 keV was constructed from the three modeled energy bins by fitting a two-section power-law model. The resulting energy-flux spectra are used to calculate atmospheric ionization rates, which provide the solar forcing from medium-energy electrons, to serve as input into long-term atmosphere and climate simulations.