Atmospheric Ion-Neutral Coupling as a Potential Driver for Saturn's Magnetospheric Antisunward Electric Field

Saturn's inner magnetosphere contains a weak antisunward electric field that has influenced a wide array of different aspects of the magnetospheric conditions in that region. Previously, these currents have been explained as being caused by magnetospheric drivers. Here, we identify an alternative source for the currents, showing that the antisunward electric field could originate within Saturn's upper atmosphere. Because Saturn's auroral region is offset toward midnight, this also offsets sub-corotating ions from Saturn's rotational pole, creating a differential flow with the surrounding thermosphere, with ions super-rotating relative to the neutral atmosphere near noon and sub-rotating relative to the neutral atmosphere near midnight. These ion motions generate antisunward ionospheric Pedersen currents that close via antisunward magnetospheric currents. The location of our sketch ion flows match with past measurements of magnetospheric ion flows, confirming the atmosphere as a potential driver, and suggesting the antisunward currents cannot explain Saturn's secondary midnight auroral arc.