Ionospheric temperature variability above Jupiter’s Great Red Spot

Abstract

<p class="Sectiontext">In 2012, ground-based observations of the dominant molecular ion in gas giant ionospheres, H<sub>3</sub><sup>+</sup>, found that Jupiter’s upper atmosphere was super-heated above its iconic Great Red Spot (GRS). Temperatures there reached 1600 K, hotter even than the auroral region. It was speculated that this GRS “hotspot” was the signature of coupling between Jupiter’s lower and upper atmosphere, perhaps associated with upward propagating acoustic or gravity waves originating from the Solar System’s most powerful storm system. Such an energy transfer could help explain why observed upper-atmospheric gas giant temperatures are all significantly warmer than simulations based solely on solar heating can explain, a discrepancy colloquially referred to as the “giant planet energy crisis”.</p> <p class="Sectiontext">Here, based on ground-based observations from 2016-2019, we report on spatial and temporal variations of H<sub>3</sub><sup>+</sup> temperature surrounding the GRS. We find that, while upper-atmospheric temperatures are still elevated above the GRS, they vary in time and are significantly cooler than in 2012. In addition, there are consistent spatial variations, with H<sub>3</sub><sup>+</sup> temperature generally highest on the western and northern edges of the GRS. We place these results in context with recent work that implicates Jupiter’s aurorae as primary sources of upper-atmospheric heating, and comment on their implications for Jupiter’s energy crisis.</p>