Characterizing High-Resolution Temporal and Spatial Changes of the EIA and ETA

In the past decade, the number of active spacecraft in Earth’s orbit has increased by over 500% with little indication of this figure decreasing. With most of these satellites located in Low Earth Orbit (LEO), it becomes critical to forecast the near-Earth conditions to predict the orbital drag, expected material deterioration, and expected spacecraft charging. The Ionosphere-Thermosphere (I-T) region, specifically between 350-550km, is a very dynamic region where temperatures and densities are highly dependent on the solar conditions. To understand and predict how the I-T region responds to different solar conditions, it is essential to first understand all the mechanisms behind the formation and evolution of the most dominant features in this region. In the low-latitude thermosphere, a feature that contributes to neutral density structure is called the Equatorial Thermosphere Anomaly (ETA). Similarly in the ionosphere, the dominant low-latitude feature is the Equatorial Ionization Anomaly (EIA). While the formation of the EIA has been well understood for decades, understanding the formation of the ETA is ongoing. There is significant coupling between these two features, which is shown in observational data in which the ETA, a neutral feature, appears to be magnetically aligned. There are several theories that attempt to best describe and reproduce the ETA, but there have been limitations in observational data to corroborate any of these theories. To validate these theories, a constellation of satellites as well as high-resolution simulations are required.

This poster focuses on characterizing the spatial and temporal changes in the EIA and ETA, which will dictate the constellation configuration necessary to observe the ion-neutral coupling between the two features. To simulate the I-T region, the High-Resolution Thermosphere Ionosphere Electrodynamics General Circulation Model (HR-TIEGCM) will be used to capture responses on the I-T system on a global scale. This model has a longitude-latitude grid resolution of 0.625°x0.625° with a timestep of 60 seconds, which is appropriate for these types of spatial-temporal analyses. The HR-TIEGCM will impose various quiet and active geomagnetic conditions to observe the evolution of the features, with particular focus on the effects of field-aligned ion drag. Once these temporal-spatial characterizations have been established, they can be used to dictate constellation coverage requirements for future missions. One relevant mission that will take in-situ measurements of the I-T region using a constellation of satellites is the NSF-funded SWARM-EX mission. This mission consists of 3 identical formation-flying satellites that will address open aeronomy questions dealing with the evolution of the EIA and ETA. SWARM-EX will look at the persistence and correlations of the EIA/ETA features and how these features evolve on suborbital periods. This multi-satellite mission, combined with the analyses from the HR-TIEGCM simulations will take the understanding of the I-T system to a resolution that has not been captured before.