  Electric currents flowing through near-Earth space ($\textit{R}$ $\leq$12
$\mathit{R}_{E}$) can support a highly distorted magnetic field topology,
changing particle drift paths and therefore having a nonlinear feedback on the
currents themselves. A number of current systems exist in the magnetosphere,
most commonly defined as (1) the dayside magnetopause Chapman-Ferraro currents,
(2) the Birkeland field-aligned currents with high latitude "region 1" and
lower-latitude "region 2" currents connected to the partial ring current, (3)
the magnetotail currents, and (4) the symmetric ring current. In the near-Earth
nightside region, however, several of these current systems flow in close
proximity to each other. Moreover, the existence of other temporal current
systems, such as the substorm current wedge or "banana" current, has been
reported. It is very difficult to identify a local measurement as belonging to
a specific system. Such identification is important, however, because how the
current closes and how these loops change in space and time governs the
magnetic topology of the magnetosphere and therefore controls the physical
processes of geospace. Furthermore, many methods exist for identifying the
regions of near-Earth space carrying each type of current. This study presents
a robust collection of these definitions of current systems in geospace,
particularly in the near-Earth nightside magnetosphere, as viewed from a
variety of observational and computational analysis techniques. The influence
of definitional choice on the resulting interpretation of physical processes
governing geospace dynamics is presented and discussed.
