Multiple Scale Structures of Dayside Current System: Joint observations by MMS, Cluster and Swarm

The conjunction of different spacecraft missions provide the opportunity to investigate the multiple scale of the magnetospheric current system. In our work, we use the data from MMS, Cluster and Swarm to study the characteristics of both the dayside current, including the magnetopause, and other current systems connected by the field aligned currents. Using the MMS four spacecraft data, we investigated the small-scale physical process of the magnetopause current, e.g. current carriers and current sources, which show features beyond the classic Chapman-Ferraro model. We compare MMS crossings to simultaneous crossings at different locations on the MP current layer observed by Cluster. Cluster is an order of magnitude lower than MMS and cannot reveal the detailed current structure due to its large separation. However, we find that the MP at the above two locations can have similar magnetic field structure. This may suggest that the MP has similar current structure across wide region during specific IMF conditions. We also used the conjunction of MMS and Swarm and Cluster and Swarm to investigate the behaviour of field-aligned currents. MMS and Swarm can calculate the current in the dayside inner low latitude boundary and the mapped ionospheric region simultaneously. Comparing the observed current signatures, we can investigate the correlation between them, which may reveal the nature of the magnetopause-ionosphere coupling between the field aligned current systems.