Local Time Asymmetries in Jupiter's Magnetodisc Currents

Lorch, Chris and Ray, Licia C and Arridge, Chris and Khurana, Krishan and Martin, Carley and Bader, Alexander (2020) Local Time Asymmetries in Jupiter's Magnetodisc Currents. Journal of Geophysical Research: Space Physics, 125 (2): e2019JA027. ISSN 2169-9402

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Abstract

We present an investigation into the currents within the Jovian magnetodisc using all available spacecraft magnetometer data up until 28th July, 2018. Using automated data analysis processes as well as the most recent intrinsic field and current disk geometry models, a full local time coverage of the magnetodisc currents using 7382 lobe traversals over 39 years is constructed. Our study demonstrates clear local time asymmetries in both the radial and azimuthal height integrated current densities throughout the current disk. Asymmetries persist within 30 R$_\mathrm{J}$ where most models assume axisymmetry. Inward radial currents are found in the previously unmapped dusk and noon sectors. Azimuthal currents are found to be weaker in the dayside magnetosphere than the nightside, in agreement with global magnetohydrodynamic simulations. The divergence of the azimuthal and radial currents indicates that downward field aligned currents exist within the outer dayside magnetosphere. The presence of azimuthal currents is shown to highly influence the location of the field aligned currents which emphasizes the importance of the azimuthal currents in future Magnetosphere-Ionosphere coupling models. Integrating the divergence of the height integrated current densities we find that 1.87 MA R$_\mathrm{J}^{-2}$ of return current density required for system closure is absent.