Dominant Trends in Jupiter's H 3 + ${\mathbf{H}}_{\mathbf{3}}^{\mathbf{+}}$ Northern Aurora: II. Magnetospheric Mapping

Abstract

Jupiter's auroral regions have previously been defined by broad-scale auroral structures, but these are typically obscured by the wide array of temporal variability observed at timescales between minutes and days, making it difficult to understand the underlying magnetospheric biases driving these brightness differences. Here, we follow on from an initial study of Jupiter's aurora, again utilizing a data set of $>$13,000 $H_3^{+}$ images of Jupiter mapped into latitude, longitude and local time, smoothed over tens of hours of integration and many days of observing. Having removed correlations between brightness and both magnetic field and planetary local time identified in the first study, we examine morphological changes in emission with both planetary and magnetic local time. We reveal that the $H_3^{+}$ main auroral emission is enhanced by a factor of three in the region mapping into the dusk magnetosphere. An additional strong auroral darkening is observed near noon, aligned with previous ultraviolet observations of an auroral discontinuity in this region, though this rotates duskward slightly in magnetic local time, as the ionospheric source mapping to this region moves duskward. The polar aurora contrasts with this strongly, showing brightness enhancement when the auroral pole points toward the dawn and dusk limbs. It also shows that the Dark region is fixed in local time, close to the dawnward edge of the polar region, while the Swirl region appears to match well with predictions from recent MHD models when the magnetic pole points toward dawn, but changes significantly at other magnetic pole directions.