A Model of the Globally-averaged Thermospheric Energy Balance

TL;DR

This paper introduces a first-principles 1D model of the thermosphere and ionosphere that incorporates detailed chemistry, energy inputs, and radiative losses, accurately reproducing observed temperature and density profiles.

Contribution

The model uniquely integrates comprehensive NO chemistry and energy balance processes, providing improved accuracy in simulating the thermospheric energy budget compared to previous models.

Findings

Exospheric temperatures within 10% of MSIS values

Peak electron densities within a factor of 2 of IRI data

Successfully reproduces NO density peak at 106 km

Abstract

The Atmospheric Chemistry and Energetics (ACE) 1D model is a first principles based model that generates a globally averaged thermosphere and ionosphere in terms of constituent major, minor, and charged species, as well as associated temperatures. The model solves the 1D continuity and energy equations representing relevant physical processes, and is supported by a chemistry scheme that reflects our current understanding of chemical processes in the region. The model is a first in its detailed treatment of Nitric oxide (NO) chemistry, including the N$_2$(A) + O reaction as a source, and accounting for chemiluminescence effects resulting from the vibrationally excited NO produced by N($^2$D, $^4$S) + O$_2$. The model utilizes globally averaged solar fluxes between 0.05-175 nm as the primary form of energy input, parameterized using the F10.7 index to reflect variations over the course of a solar cycle. The model also includes joule heating effects, magnetospheric fluxes, and a parameterized treatment of photoelectron effects as secondary heating sources. The energy inputs are balanced by radiative losses from the neutral thermosphere in the form of infrared emissions from CO$_2$, NO and O($^3$P). Atmospheric profiles are generated for a solar cycle, and are compared with empirical model results as well as observational data. On average, calculated exospheric temperatures are within 10% of MSIS values, while peak electron densities are within a factor of 2 of IRI values. The model is shown to reproduce the NO peak at 106 km, and densities within 25% of globally averaged satellite measurements.