The Norwegian Cluster studies 2014-2016

Cluster is a European Space Agency (ESA) multi-satellite project launched in 2000 to study the terrestrial magnetosphere and its boundary regions. Norwegian space science groups at the University of Bergen (UiB), the University of Oslo (UiO) and the Norwegian Defense Research Establishment (FFI) have taken part in this project since the beginning. Norwegian activities in this project have been supported by the Norwegian Research Council for the years 2014-2017. Space research in Norway utilizing Cluster data has focussed on two main topics the last few years: 1) Asymmetries of large scale current system in the magnetosphere and 2) Outflow of cold plasma from the polar regions. The research has provided new insight and knowledge about our near Earth space environments. One of the most interesting results from these studies are the discoveries and characterizations of persistent asymmetries in the magnetosphere. Using 14 years of Cluster data from the magnetopause (a distinct boundary between the solar wind and geomagnetic field), we found a persistent dawn-dusk asymmetry: The dusk flank is thinner and has a higher current density than its dawn counterpart. Similar asymmetries were also found in the outflow of cold plasma from the polar cap regions. Here, 16 years of Cluster data was used to characterize the plasma density in the magnetotail lobes (a region of the magnetosphere magnetically connected to the polar cap regions). Northern hemisphere plasma densities were persistently higher than the corresponding southern hemisphere density. Since the source of the measured plasma is the polar ionosphere, the results indicate an asymmetric outflow of plasma from the two hemispheres. Differences in illumination and/or magnetic field onfigurations can explain parts of the asymmetry, but this study will be followed up to investigate other possible sources of the asymmetry.

This is a joint project submitted by researchers from the University of bergen (UiB), the University of Oslo (UiO) to support and maintain the existing Norwegian Cluster studies for 2014-2016. The main themes of the proposal are the study of ionospheric o utflow and the coupling between different current systems. We plan to utilize the large data set obtained by the Cluster spacecraft during the last 11 years, and also combine these with with ground based data. Science issues to be addressed are closely r elated to the primary objectives of the Cluster mission and future multi-spacecraft missions. Many members of the team are Co-investigators of several of the experiments onboard Cluster, and are international recognized specialists within their field. T he Norwegian team will focus on themes where we have strong experience and expertise and can make significant contribution to the space science community. Among the themes we plan to address are the solar wind and solar radiance control on ionospheric o utflow and plasma transport, the fate of cold ions escaping from the polar cap ionosphere and the coupling of different current systems in the magnetosphere. The proposed project will provide young scientists (PostDocs, PhD stdents and Master students) an opportunity to work in a team of experienced scientists. Cluster is also a highly international mission, and the project will strengthen our collaboration with the top science communities all over the world.