Examining Ionization Parameterizations for Energetic Electrons in the Ionosphere Using TIME-GCM Simulations

Energetic electrons in the upper atmosphere influence atmospheric dynamics and ionize chemical species—which ultimately affects the atmosphere's chemical composition. Two important chemical constituents affected by electron ionization are HOx and NOx, whose presence and mechanisms contribute to ozone destruction. Therefore, energetic particles have an important influence on the dynamical and chemical processes in the upper atmosphere. The Thermosphere-Ionosphere-Mesosphere Electrodynamics General Circulation Model (TIME-GCM) has been developed at the National Center for Atmospheric Research (NCAR) to study the upper atmosphere at altitudes between 30 and 500 km. Currently, TIME-GCM only includes effects from lower-energy auroral electrons (those with energies less than 30 keV). The purpose of this study is to incorporate higher-energy electrons (those with energies greater than 30 keV) into the model and investigate their effects on the upper atmosphere. In order to accurately represent these higher-energy electrons, two parameterization codes have been tested in TIME-GCM. The first parameterization code applies a Maxwellian distribution while the second uses in-situ measurements of electron distribution from which it calculates ionization rates. The test runs were then compared with base runs that did not contain either parameterization, and were also compared with satellite measurements. Overall the second parameterization code produces higher neutral temperatures and NO values that are in better agreement with satellite observations, making it a more accurate representation. Model improvements such as these are crucial to improve simulations of the upper atmosphere and for understanding the mechanics in this region.