Geospace electrodynamic connections

Abstract

As part of NASA's Solar Terrestrial Probe (STP) line of spacecraft, the planned Geospace Electrodynamic Connections (GEC) mission is designed to finally explore in depth the intricacies of electrodynamic coupling processes in the lower ionosphere, where magnetospheric processes couple with the thermosphere. It is currently envisioned as a 4-spacecraft (identically instrumented) mission, which will measure all relevant in situ plasma and neutral atmosphere parameters with the option of including remote observations for a wider perspective. The parking orbits will be 200X2000 km with weeklong dipping campaigns planned down below 130 km where the neutral atmosphere begins to dominate the dissipation of plasma energy and momentum. Each spacecraft will carry hundreds of kilograms of propellant to enable deep dipping campaigns and to have the maneuverability to investigate a broad spectrum of relevant electrodynamic coupling scale sizes. Thruster firings will be used to provide different spacings between spacecraft - either along a common pearls-on-a-string configuration, or by separating the planes of the orbits in local time, or by relative changes in the latitude of the argument of perigee. GEC has the exciting potential for resolving many of the uncertainties in our understanding of the ionosphere as an inseparable part of the electrodynamic physics chain connecting the sun's magnetoplasma with the Earth's upper atmosphere.