Challenges in Measuring External Currents Driven by the Solar Wind-Magnetosphere Interaction

摘要

In studying the Earth's geomagnetism it has always been a challenge to separate the external currents originating from the ionosphere and magnetosphere. While the internal magnetic field changes very slowly in time scales of years and more, the ionospheric and magnetospheric current systems driven by the solar wind-magnetosphere interaction are very dynamic. They are intimately controlled by the ionospheric electrodynamics and ionosphere-magnetosphere coupling. Single spacecraft observations are not able to separate their spatial and temporal variations, and thus to accurately describe their configurations. To characterize and understand the external currents, satellite observations require both good spatial and temporal resolutions. This paper reviews our observations of the external currents from two recent Low Earth Orbit (LEO) satellite missions: Space Technology 5 (ST-5), NASA's first three-satellite constellation mission in LEO polar orbit and Communications/Navigation Outage Forecasting System (C/NOFS), an equatorial satellite developed by the US Air Force Research Laboratory. We present recommendations for future geomagnetism missions based on these observations.