  When the solar wind interacts with the ionosphere of an unmagnetized planet,
it induces currents that form an induced magnetosphere. These currents and
their associated magnetic fields play a pivotal role in controlling the
movement of charged particles, which is essential for understanding the escape
of planetary ions. Unlike the well-documented magnetospheric current systems,
the ionospheric current systems on unmagnetized planets remain less understood,
which constrains the quantification of electrodynamic energy transfer from
stars to these planets. Here, utilizing eight years of data from the Mars
Atmosphere and Volatile EvolutioN (MAVEN) mission, we investigate the global
distribution of ionospheric currents on Mars. We have identified two distinct
current systems in the ionosphere: one aligns with the solar wind electric
field yet exhibits hemispheric asymmetry perpendicular to the electric field
direction; the other corresponds to the flow pattern of annually-averaged
neutral winds. We propose that these two current systems are driven by the
solar wind and atmospheric neutral winds, respectively. Our findings reveal
that Martian ionospheric dynamics are influenced by the neutral winds from
below and the solar wind from above, highlighting the complex and intriguing
nature of current systems on unmagnetized planets.
