Preliminary JIRAM results from Juno polar observations: 2. Analysis of the Jupiter southern H₃⁺ emissions and comparison with the north aurora

Abstract

The Jupiter InfraRed Auroral Mapper (JIRAM) aboard Juno observed the Jovian South Pole aurora during the first orbit of the mission. H3+ (trihydrogen cation) and CH4 (methane) emissions have been identified and measured. The observations have been carried out in nadir and slant viewing both by a L‐filtered imager and a 2–5 μm spectrometer. Results from the spectral analysis of the all observations taken over the South Pole by the instrument are reported. The coverage of the southern aurora during these measurements has been partial, but sufficient to determine different regions of temperature and abundance of the H3+ ion from its emission lines in the 3–4 μm wavelength range. Finally, the results from the southern aurora are also compared with those from the northern ones from the data taken during the same perijove pass and reported by Dinelli et al. (2017).

Mapping H3+ Temperatures in Jupiter's Northern Auroral Ionosphere Using VLT‐CRIRES

“…It could be the case that the aurora as a whole experienced local time differences. As discussed in section 4, the H 3 + temperature structure measured in this present study are in agreement with those measured by Moore et al () but not Adriani et al (). Moore et al () measured the dayside auroral temperatures at local times similar to those presented in this study.…”

“…No overall anticorrelation is seen in Figure c either, which shows the relationship between the temperature and column density. The recent study of Adriani et al (), which uses Juno‐JIRAM data, also shows no evidence of anticorrelation between the temperature and column density, in agreement with the present study. Therefore, H 3 + is not an efficient thermostat across the entire auroral region.…”

“…Figure a shows that there is a strong positive correlation between the total emission (Figure c) and the column density (Figure b). Other studies, such as Stallard et al (), Moore et al (), and Adriani et al (), also noted this correlation, and it implies that the ionization rate governs the intensity. While enhancements in H 3 + total emission could also be caused by increases in temperature of the ionosphere, only a modest correlation between the total emission (Figure c) and the temperature (Figure a) was observed in Figure b.…”

Infrared observations of Jovian aurora from Juno's first orbits: Main oval and satellite footprints

“…The southern aurora appears significantly brighter at the time of observation (~50% higher intensity), as found in the spectrometer measurements [ Adriani et al ., ; Dinelli et al ., ]. Three or four diffuse emission spots, placed at 0° System III west longitude and outside the main oval in the south, are visible in the spectrometer data as well and can be linked with similar features in the north aurora at 0° longitude; these may be signatures of plasma injections [ Mauk et al ., ; Dumont et al ., ].…”

Preliminary JIRAM results from Juno polar observations: 3. Evidence of diffuse methane presence in the Jupiter auroral regions

“…The spatial distribution and temperature of the 3.3 μm CH 4 emission have been derived from the spectral data, while the L band images have been used to verify and provide the global context and location of the emitting molecules [see Adriani et al ., , Figure 1].…”