Evaluating Multipoint Sampling of Global-Scale High-Latitude Electrodynamics by the Geospace Dynamics Constellation

Abstract

The Geospace Dynamics Constellation (GDC) mission aims to investigate the dynamic coupling between the magnetosphere, ionosphere, and thermosphere by resolving key spatiotemporal processes at scales ranging from local to global. A key aspect is GDC's ability to reconstruct hemispheric-scale high-latitude electrodynamics with comprehensive measurements at multiple local times. This study evaluates the accuracy of GDC reconstructions of electric potential (PHI) and Joule Heating (JH) derived from the AMPERE-derived electrodynamic properties of the high-latitude ionosphere (ADELPHI) and Weimer 2005 models by comparing them to the original model outputs used as ground truth. Accuracy is assessed across four selected geomagnetic storm events with GDC reconstructions spanning from Day 91 after GDC launch to the end of the mission using a 20-day cadence. As the mission progresses, the constellation evolves into three well-separated orbital pairs with increasing local time separation, significantly improving the PHI and JH reconstruction accuracy. To assess accuracy, we compute several performance metrics. Results from both models show that for the specific application of reconstructing large-scale high-latitude electrodynamics, performance metrics improve over mission time as the constellation evolves, reflecting better sampling and constraint for the reconstructions. Notably, however, even during the early mission stage, reconstructions can sometimes be as accurate as in the later stage, depending on the fortuitous sampling of appropriate local time sectors. This quantitative assessment underscores the critical role of orbital geometry and sampling diversity in fulfilling GDC's science objectives and advancing the understanding of space weather dynamics. It also provides a tool for optimizing the GDC orbital characteristics.