Cluster Multi-Probing of the Aurora During Two Decades

摘要

The Cluster spacecraft, launched in the year 2000, were pioneers using multi-point measurements to explore the dynamic space plasma environment of Earth. This capability offered a new, powerful approach to study in situ fundamental space plasma processes of the solar-terrestrial interaction. Although not a major science objective of the mission, the aurora and associated processes proved to be a very fruitful target for exploration by the Cluster fleet. Here, results are presented from a selection of Cluster auroral studies using the multi-point measurements capability to further our understanding on various open issues on the aurora. These include the nature and properties of the auroral acceleration region, in particular the altitude distribution of the quasi-static parallel electric field and potential, the auroral density cavity and its relation to the acceleration region, the role of and relative contribution by quasi-static and Alfvénic acceleration processes in producing aurora. A related topic addressed by Cluster is acceleration processes and dynamics of the downward current region and its relation to black aurora. To get a broader perspective on these phenomena, event and statistical studies were used, supported by, in a few cases, numerical simulation studies.