A new composite of energetic electron precipitation and resulting atmospheric ionization based on combined POES and Proba-V data

The long observational record of POES satellites (1979 to present) is often used to estimate the EEP and study its long-term evolution and atmospheric impacts. The unique POES record has been the basis for the CMIP6 and CMIP7 versions of the EEP forcing recommended as an input to chemistry-climate models. While the POES measurements provide a long and nearly continuous data series they suffer, among other things, from poor energy resolution. They measure the energetic electrons with 3 integral channels spanning from >30 keV, >100 keV to >300 keV.

There are strong indications that the relativistic part of the EEP spectrum, largely missed by the POES observations, is likely to be important because of the direct ionization it produces in the mesosphere. Typically, the high-energy part of the EEP spectrum is estimated by a power-law extrapolation from lower energies, but this might not be accurate.

Here we present preliminary results combining the recently homogenized record of POES observations to another record of energetic electron measurements made at low-Earth orbit by the Proba-V satellite during 2013-present. Together these measurements cover energies from 30 keV to 8 MeV. We describe here the construction of the dataset and the methods used to join the Proba-V measured spectra to the spectra measured by POES, and finally evaluate the resulting atmospheric ionization.