Local time variations in Jupiter's magnetosphere‐ionosphere coupling system

Abstract The ionization of neutral material ejected by Jupiter's volcanically active moon, Io, results in a plasma disc that extends from Io's orbit out through the Jovian magnetosphere. This magnetospheric plasma is coupled to the planetary ionosphere via currents which flow along the magnetic field. Inside of ∼40 R J , these currents transfer angular momentum from the planet to the magnetospheric plasma, in an attempt to keep the plasma rigidly corotating with the planet. Jupiter's main auroral emission is a signature of this current system. To date, one‐dimensional models of Jupiter's magnetosphere‐ionosphere (M‐I) coupling have either assumed a dipole field or used a field description appropriate to the postmidnight region of the Jovian magnetosphere. Vogt et al. (2011) described the variation of the N‐S component of the magnetic field in the center of the current sheet, B N , with local time and radius. We apply a 1‐D model of Jupiter's M‐I current system every hour in local time using a modified description of the Vogt et al. (2011) magnetic field to investigate how local time variations in the magnetosphere affect the auroral currents and plasma angular velocity. Our model predicts the strongest aurora at dawn, with a minimum in the auroral currents existing from noon through dusk. This is a few hours duskward of the discontinuity predicted by Radioti et al. (2008). While our model predictions are consistent with some of the observations, future MI coupling models must account for the azimuthal bendback in the magnetic field.