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.