Correspondence between field aligned currents observed by Ulysses and HST auroral emission

Abstract

Auroral emission is direct evidence for the magnetophere/ionosphere coupling which exists for a magnetised planet such as Jupiter. This coupling takes place by way of momentum transfer which occurs via field aligned currents. The driving mechanism for the auroral emission is charged particle precipitation along the field lines. During the Ulysses flyby of Jupiter in February 1992 high latitude auroral events were recorded by the Faint Object Camera on the Hubble Space Telescope using direct imaging of UV emissions. Measurements of magnetospheric field aligned current signatures were recorded by the dual fluxgate/vector helium magnetometer onboard the Ulysses spacecraft on the same day as the auroral, emissions. A correspondence is found to occur between the locus of auroral emission on Jupiter and the oval traced onto the auroral region by projection of the observed interval of field aligned currents. The field line mapping used to establish this correspondence is performed using a magnetospheric field model tailored to the conditions observed during the Ulysses flyby.