The role of the Hall effect in the global structure and dynamics of planetary magnetospheres: Ganymede as a case study

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 J × B forces accelerate ions to the local Alfvén 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 Alfvénic ion jet extending across the upstream magnetopause, and an asymmetric pattern of magnetopause Kelvin‐Helmholtz waves.Key PointsThe Hall effect produces a new system of FAC directly generated by reconnectionThe Hall effect produces a new system of ion drift beltsEvidence of the Hall effect is seen in the Galileo G8 flybyPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113113/1/jgra51770.pd