Abstract
AbstractThe 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 RJ, 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, BN, 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.
Highlights
Jupiter’s main auroral oval is the most persistent auroral emission in the solar system, driven by corotation enforcement currents that couple the planetary ionosphere to the middle magnetospheric plasma
The latitudinal extent of the UV main auroral emission is on the order of ∼1–3◦ and its Jovicentric location is steady, with variations of only ∼3◦ that are possibly driven by changes in solar wind and/or internal magnetospheric plasma conditions [Grodent et al, 2008a]
We derive an analytic expression for the magnetic flux function at the planet as a function of latitude and local time assuming a dipole field. This simplifying assumption, which ignores the azimuthal bendback in the magnetospheric field and higher-order moments at the planet, allows us to determine the suitability of employing 1-D slices that vary in local time in future magnetosphere-ionosphere-thermosphere coupling studies
Summary
Jupiter’s main auroral oval is the most persistent auroral emission in the solar system, driven by corotation enforcement currents that couple the planetary ionosphere to the middle magnetospheric plasma. We use the Vogt et al [2011] description of the component of the magnetospheric magnetic field normal to the current sheet, BN, modified to extend into 5 RJ, coupled with a Hill-like 1-D model of the auroral currents, constructed under simplified assumptions—constant ionospheric Pedersen conductance, equipotential field aCoefficients defined lines, and a dipole field at Jupiter—to investigate how variations in the magin Vogt et al [2011]. We derive an analytic expression for the magnetic flux function at the planet as a function of latitude and local time assuming a dipole field This simplifying assumption, which ignores the azimuthal bendback in the magnetospheric field and higher-order moments at the planet, allows us to determine the suitability of employing 1-D slices that vary in local time in future magnetosphere-ionosphere-thermosphere coupling studies.
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