ECLAT Cluster Spacecraft Magnetotail Plasma Region Identifications (2001–2009)

The European Space Agency’s four-spacecraft Cluster mission has been observing the Earth’s dynamical magnetotail region since early 2001. The magnetotail, and in particular the hot trapped plasma sheet, is a critical region in the coupled Sun-Earth system. Changes in the solar wind have direct influence on the properties and dynamical processes occurring in this region, which in turn directly influence operational near-Earth space, the upper atmosphere, and even induce large-scale currents in the ground. As part of the European Cluster Assimilation Technology (ECLAT) project, a magnetotail plasma region dataset has been produced to facilitate magnetospheric research and further our understanding of the important processes linking the solar wind-magnetospheric-ionospheric system. The dataset consists of a comprehensive list of plasma regions encountered in the nightside magnetosphere of the Earth by each of the four Cluster spacecraft in the years 2001–2009. The regions identified are those where major energy transport/conversion processes take place and are important regions for system level science. Characteristic averaged parameters describing the behavior of each region are provided for further understanding. The dataset facilitates the use of the large repository of Cluster data by the wider scientific community. 1. Introduction The plasma environment of the Earth’s magnetosphere (the region of near-Earth space governed by the Earth’s magnetic field) provides an excellent natural laboratory to study fundamental plasma physics processes. Knowledge gained through the study of changes in this environment, and its dependence on Sun-Earth interactions, is important for satellite operation as well as understanding environmental and technological impacts on the surface of Earth (i.e., space weather). The fundamental interaction process resulting in the plasma environment at the Earth is the so-called Dungey cycle [1]. On the dayside of the Earth previously closed (with both footprints connected to the Earth) terrestrial magnetic field lines are split into two open magnetic field lines (with one footprint connected to the northern or southern hemisphere of the Earth, respectively, and the other connected to the solar wind) by magnetic reconnection. Solar wind particles can gain access to the Earth’s magnetosphere through the high latitude open cusp regions. The opened magnetic field lines are swept by the solar wind flow to the nightside of the Earth, where they come together in the distant magnetotail and reconnect to form a newly closed magnetic field