Fig. 2: Plot showing the temporal characteristics of different components of the \({{\rm{H}}}_{3}^{+}\) emission.
a Shows the mean of the line-of-sight corrected radiance 〈Lc〉 from regions in the dusk active region (DAR, red), the noon active region (NAR, black), the Swirl region (blue), the dark polar region (DPR, turquoise), and the main emission (ME, orange) versus UT time over the whole observation interval. b Shows line-of-sight corrected radiance Lc from a representative image from observation NIRCam3104 projected onto a spheroid 500 km above the 1-bar level and plotted in a polar stereographic projection. The regions from which the 〈Lc〉 values are computed are shown by the labelled cyan boxes. A 20° × 10° graticule is overlaid in grey, along with solid lines which show the mapped moon footprints (respectively, with increasing latitude Io, Europa and Ganymede)67 and reference main oval42 (cyan dotted line). The coordinate system is planetocentric, labelled with System III westward longitude. The central meridian longitude (here 153.78∘) is oriented toward the bottom. Source data for (a) are provided as a Source Data file, and source data for (b) are available on Figshare66.
