  We present high resolution Hall MHD simulations of Ganymede's magnetosphere
demonstrating that Hall electric fields in ion-scale magnetic reconnection
layers have significant global effects not captured in resistive MHD
simulations. Consistent with local kinetic simulations of magnetic
reconnection, our global simulations show the development of intense
field-aligned currents along the magnetic separatrices. These currents extend
all the way down to the moon's surface, where they may contribute to Ganymede's
aurora. Within the magnetopause and magnetotail current sheets, Hall currents
in the reconnection plane accelerate ions to the local Alfv\'en speed in the
out-of-plane direction, producing a global system of ion drift belts that
circulates Jovian magnetospheric plasma throughout Ganymede's magnetosphere. We
discuss some observable consequences of these Hall-induced currents and ion
drifts: the appearance of a sub-Jovian "double magnetopause" structure, an
Alfv\'enic ion jet extending across the upstream magnetopause and an asymmetric
pattern of magnetopause Kelvin-Helmholtz waves.
